New JTAG driver for Versaloon

This patch greatly simplifies the Versaloon driver:

 - reducing the code size from more than 50K to less than 28K
 - adding support for IR/DR scan with unlimited size
 - using tap_get_tms_path and tap_get_tms_path_len.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

1 files changed, 304 insertions, 1072 deletions

diff --git a/src/jtag/drivers/vsllink.c b/src/jtag/drivers/vsllink.c
index 65c3bf17..451d5f8f 100644
--- a/src/jtag/drivers/vsllink.c
+++ b/src/jtag/drivers/vsllink.c
@@ -1,5 +1,5 @@
 /***************************************************************************
- *   Copyright (C) 2009 by Simon Qian <SimonQian@SimonQian.com>            *
+ *   Copyright (C) 2009-2010 by Simon Qian <SimonQian@SimonQian.com>       *
  *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
  *   it under the terms of the GNU General Public License as published by  *
@@ -18,7 +18,7 @@
  ***************************************************************************/
 
 /* Versaloon is a programming tool for multiple MCUs.
- * OpenOCD and MSP430 supports are distributed under GPLv2.
+ * It's distributed under GPLv3.
  * You can find it at http://www.SimonQian.com/en/Versaloon.
  */
 
@@ -32,179 +32,85 @@
 
 //#define _VSLLINK_IN_DEBUG_MODE_
 
-#define VSLLINK_MODE_NORMAL			0
-#define VSLLINK_MODE_DMA			1
-
 static uint16_t vsllink_usb_vid;
 static uint16_t vsllink_usb_pid;
-static uint8_t vsllink_usb_bulkout;
-static uint8_t vsllink_usb_bulkin;
-static uint8_t vsllink_usb_interface;
-static uint8_t vsllink_mode = VSLLINK_MODE_NORMAL;
-static int VSLLINK_USB_TIMEOUT = 10000;
+static uint8_t  vsllink_usb_bulkout;
+static uint8_t  vsllink_usb_bulkin;
+static uint8_t  vsllink_usb_interface;
+static int      VSLLINK_USB_TIMEOUT = 1000;
 
-static int VSLLINK_BufferSize = 1024;
+static int vsllink_tms_offset = 0;
 
 /* Global USB buffers */
-static int vsllink_usb_out_buffer_idx;
-static int vsllink_usb_in_want_length;
-static uint8_t* vsllink_usb_in_buffer = NULL;
+static uint8_t* vsllink_usb_in_buffer  = NULL;
 static uint8_t* vsllink_usb_out_buffer = NULL;
+static int      vsllink_buffer_size    = 128;
 
-/* Constants for VSLLink command */
-#define VSLLINK_CMD_CONN			0x80
-#define VSLLINK_CMD_DISCONN			0x81
-#define VSLLINK_CMD_SET_SPEED		0x82
-#define VSLLINK_CMD_SET_PORT		0x90
-#define VSLLINK_CMD_GET_PORT		0x91
-#define VSLLINK_CMD_SET_PORTDIR		0x92
-#define VSLLINK_CMD_HW_JTAGSEQCMD	0xA0
-#define VSLLINK_CMD_HW_JTAGHLCMD	0xA1
-#define VSLLINK_CMD_HW_SWDCMD		0xA2
-#define VSLLINK_CMD_HW_JTAGRAWCMD	0xA3
-
-#define VSLLINK_CMDJTAGSEQ_TMSBYTE	0x00
-#define VSLLINK_CMDJTAGSEQ_TMSCLOCK	0x40
-#define VSLLINK_CMDJTAGSEQ_SCAN		0x80
-
-#define VSLLINK_CMDJTAGSEQ_CMDMSK	0xC0
-#define VSLLINK_CMDJTAGSEQ_LENMSK	0x3F
-
-#define JTAG_PINMSK_SRST			(1 << 0)
-#define JTAG_PINMSK_TRST			(1 << 1)
-#define JTAG_PINMSK_USR1			(1 << 2)
-#define JTAG_PINMSK_USR2			(1 << 3)
-#define JTAG_PINMSK_TCK				(1 << 4)
-#define JTAG_PINMSK_TMS				(1 << 5)
-#define JTAG_PINMSK_TDI				(1 << 6)
-#define JTAG_PINMSK_TDO				(1 << 7)
-
-
-#define VSLLINK_TAP_MOVE(from, to)	VSLLINK_tap_move[tap_move_ndx(from)][tap_move_ndx(to)]
-
-/* VSLLINK_tap_move[i][j]: tap movement command to go from state i to state j
- * 0: Test-Logic-Reset
- * 1: Run-Test/Idle
- * 2: Shift-DR
- * 3: Pause-DR
- * 4: Shift-IR
- * 5: Pause-IR
- *
- * SD->SD and SI->SI have to be caught in interface specific code
- */
-static uint8_t VSLLINK_tap_move[6][6] =
-{
-/*	  TLR   RTI   SD    PD    SI    PI             */
-	{0xff, 0x7f, 0x2f, 0x0a, 0x37, 0x16},	/* TLR */
-	{0xff, 0x00, 0x45, 0x05, 0x4b, 0x0b},	/* RTI */
-	{0xff, 0x61, 0x00, 0x01, 0x0f, 0x2f},	/* SD  */
-	{0xfe, 0x60, 0x40, 0x5c, 0x3c, 0x5e},	/* PD  */
-	{0xff, 0x61, 0x07, 0x17, 0x00, 0x01},	/* SI  */
-	{0xfe, 0x60, 0x38, 0x5c, 0x40, 0x5e}	/* PI  */
-};
-
-struct insert_insignificant_operation {
-	unsigned char insert_value;
-	unsigned char insert_position;
-};
-
-static struct insert_insignificant_operation VSLLINK_TAP_MOVE_INSERT_INSIGNIFICANT[6][6] =
-{
-/*	 stuff	offset   */
-	{/*	TLR	*/
-	{1,		0,},	/* TLR */
-	{1,		0,},	/* RTI */
-	{1,		0,},	/* SD  */
-	{1,		0,},	/* PD  */
-	{1,		0,},	/* SI  */
-	{1,		0,}},	/* PI  */
-	{/*	RTI	*/
-	{1,		0,},	/* TLR */
-	{0,		0,},	/* RTI */
-	{0,		4,},	/* SD  */
-	{0,		7,},	/* PD  */
-	{0,		5,},	/* SI  */
-	{0,		7,}},	/* PI  */
-	{/*	SD	*/
-	{0,		0,},	/* TLR */
-	{0,		0,},	/* RTI */
-	{0,		0,},	/* SD  */
-	{0,		0,},	/* PD  */
-	{0,		0,},	/* SI  */
-	{0,		0,}},	/* PI  */
-	{/*	PD	*/
-	{0,		0,},	/* TLR */
-	{0,		0,},	/* RTI */
-	{0,		0,},	/* SD  */
-	{0,		0,},	/* PD  */
-	{0,		0,},	/* SI  */
-	{0,		0,}},	/* PI  */
-	{/*	SI	*/
-	{0,		0,},	/* TLR */
-	{0,		0,},	/* RTI */
-	{0,		0,},	/* SD  */
-	{0,		0,},	/* PD  */
-	{0,		0,},	/* SI  */
-	{0,		0,}},	/* PI  */
-	{/*	PI	*/
-	{0,		0,},	/* TLR */
-	{0,		0,},	/* RTI */
-	{0,		0,},	/* SD  */
-	{0,		0,},	/* PD  */
-	{0,		0,},	/* SI  */
-	{0,		0,}},	/* PI  */
-};
+/* Constants for Versaloon command */
+#define VERSALOON_GET_INFO				0x00
+#define VERSALOON_GET_TVCC				0x01
 
-static uint8_t VSLLINK_BIT_MSK[8] =
-{
-	0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f
-};
+/* Constants for VSLLink command */
+#define VSLLINK_CMD_CONN				0x80
+#define VSLLINK_CMD_DISCONN				0x81
+#define VSLLINK_CMD_SET_SPEED			0x82
+#define VSLLINK_CMD_SET_PORT			0x90
+#define VSLLINK_CMD_GET_PORT			0x91
+#define VSLLINK_CMD_SET_PORTDIR			0x92
+#define VSLLINK_CMD_HW_JTAGSEQCMD		0xA0
+#define VSLLINK_CMD_HW_JTAGHLCMD		0xA1
+#define VSLLINK_CMD_HW_SWDCMD			0xA2
+#define VSLLINK_CMD_HW_JTAGRAWCMD		0xA3
+
+#define VSLLINK_CMDJTAGSEQ_TMSBYTE		0x00
+#define VSLLINK_CMDJTAGSEQ_TMSCLOCK		0x40
+#define VSLLINK_CMDJTAGSEQ_SCAN			0x80
+
+#define VSLLINK_CMDJTAGSEQ_CMDMSK		0xC0
+#define VSLLINK_CMDJTAGSEQ_LENMSK		0x3F
+
+#define JTAG_PINMSK_SRST				(1 << 0)
+#define JTAG_PINMSK_TRST				(1 << 1)
+#define JTAG_PINMSK_USR1				(1 << 2)
+#define JTAG_PINMSK_USR2				(1 << 3)
+#define JTAG_PINMSK_TCK					(1 << 4)
+#define JTAG_PINMSK_TMS					(1 << 5)
+#define JTAG_PINMSK_TDI					(1 << 6)
+#define JTAG_PINMSK_TDO					(1 << 7)
 
 struct pending_scan_result {
-	int offset;
+	int src_offset;
+	int dest_offset;
 	int length; /* Number of bits to read */
 	struct scan_command *command; /* Corresponding scan command */
 	uint8_t *buffer;
+	bool last; /* indicate the last scan pending */
 };
 
 #define MAX_PENDING_SCAN_RESULTS 256
 
 static int pending_scan_results_length;
-static struct pending_scan_result pending_scan_results_buffer[MAX_PENDING_SCAN_RESULTS];
+static struct pending_scan_result \
+						pending_scan_results_buffer[MAX_PENDING_SCAN_RESULTS];
 
 /* Queue command functions */
 static void vsllink_end_state(tap_state_t state);
-static void vsllink_state_move_dma(void);
-static void vsllink_state_move_normal(void);
-static void (*vsllink_state_move)(void);
-static void vsllink_path_move_dma(int num_states, tap_state_t *path);
-static void vsllink_path_move_normal(int num_states, tap_state_t *path);
-static void (*vsllink_path_move)(int num_states, tap_state_t *path);
+static void vsllink_state_move(void);
+static void vsllink_path_move(int num_states, tap_state_t *path);
 static void vsllink_runtest(int num_cycles);
-static void vsllink_stableclocks_dma(int num_cycles, int tms);
-static void vsllink_stableclocks_normal(int num_cycles, int tms);
-static void (*vsllink_stableclocks)(int num_cycles, int tms);
-static void vsllink_scan_dma(bool ir_scan, enum scan_type type, uint8_t *buffer, int scan_size, struct scan_command *command);
-static void vsllink_scan_normal(bool ir_scan, enum scan_type type, uint8_t *buffer, int scan_size, struct scan_command *command);
-static void (*vsllink_scan)(bool ir_scan, enum scan_type type, uint8_t *buffer, int scan_size, struct scan_command *command);
+static void vsllink_stableclocks(int num_cycles, int tms);
+static void vsllink_scan(bool ir_scan, enum scan_type type, uint8_t *buffer, \
+							int scan_size, struct scan_command *command);
 static void vsllink_reset(int trst, int srst);
 static void vsllink_simple_command(uint8_t command);
-static int vsllink_connect(void);
-static int vsllink_disconnect(void);
 
 /* VSLLink tap buffer functions */
 static void vsllink_tap_append_step(int tms, int tdi);
-static void vsllink_tap_init_dma(void);
-static void vsllink_tap_init_normal(void);
-static void (*vsllink_tap_init)(void);
-static int vsllink_tap_execute_dma(void);
-static int vsllink_tap_execute_normal(void);
-static int (*vsllink_tap_execute)(void);
-static void vsllink_tap_ensure_space_dma(int scans, int length);
-static void vsllink_tap_ensure_space_normal(int scans, int length);
-static void (*vsllink_tap_ensure_space)(int scans, int length);
-static void vsllink_tap_append_scan_dma(int length, uint8_t *buffer, struct scan_command *command);
-static void vsllink_tap_append_scan_normal(int length, uint8_t *buffer, struct scan_command *command, int offset);
+static void vsllink_tap_init(void);
+static int  vsllink_tap_execute(void);
+static void vsllink_tap_ensure_pending(int scans);
+static void vsllink_tap_append_scan(int length, uint8_t *buffer, \
+									struct scan_command *command);
 
 /* VSLLink lowlevel functions */
 struct vsllink {
@@ -213,7 +119,8 @@ struct vsllink {
 
 static struct vsllink *vsllink_usb_open(void);
 static void vsllink_usb_close(struct vsllink *vsllink);
-static int vsllink_usb_message(struct vsllink *vsllink, int out_length, int in_length);
+static int vsllink_usb_message(struct vsllink *vsllink, int out_length, \
+								int in_length);
 static int vsllink_usb_write(struct vsllink *vsllink, int out_length);
 static int vsllink_usb_read(struct vsllink *vsllink);
 
@@ -221,29 +128,17 @@ static int vsllink_usb_read(struct vsllink *vsllink);
 static void vsllink_debug_buffer(uint8_t *buffer, int length);
 #endif
 
-static int vsllink_tms_data_len = 0;
-static uint8_t* vsllink_tms_cmd_pos;
-
 static int tap_length = 0;
 static int tap_buffer_size = 0;
 static uint8_t *tms_buffer = NULL;
 static uint8_t *tdi_buffer = NULL;
 static uint8_t *tdo_buffer = NULL;
-static int last_tms;
 
 static struct vsllink* vsllink_handle = NULL;
 
 static void reset_command_pointer(void)
 {
-	if (vsllink_mode == VSLLINK_MODE_NORMAL)
-	{
-		vsllink_usb_out_buffer[0] = VSLLINK_CMD_HW_JTAGSEQCMD;
-		vsllink_usb_out_buffer_idx = 3;
-	}
-	else
-	{
-		tap_length = 0;
-	}
+	tap_length = 0;
 }
 
 static int vsllink_execute_queue(void)
@@ -253,7 +148,9 @@ static int vsllink_execute_queue(void)
 	enum scan_type type;
 	uint8_t *buffer;
 
-	DEBUG_JTAG_IO("--------------------------------- vsllink -------------------------------------");
+	DEBUG_JTAG_IO(	"-------------------------------------"
+					" vsllink "
+					"-------------------------------------");
 
 	reset_command_pointer();
 	while (cmd != NULL)
@@ -261,15 +158,17 @@ static int vsllink_execute_queue(void)
 		switch (cmd->type)
 		{
 			case JTAG_RUNTEST:
-				DEBUG_JTAG_IO("runtest %i cycles, end in %s", cmd->cmd.runtest->num_cycles, \
-					tap_state_name(cmd->cmd.runtest->end_state));
+				DEBUG_JTAG_IO("runtest %i cycles, end in %s", \
+								cmd->cmd.runtest->num_cycles, \
+								tap_state_name(cmd->cmd.runtest->end_state));
 
 				vsllink_end_state(cmd->cmd.runtest->end_state);
 				vsllink_runtest(cmd->cmd.runtest->num_cycles);
 				break;
 
 			case JTAG_STATEMOVE:
-				DEBUG_JTAG_IO("statemove end in %s", tap_state_name(cmd->cmd.statemove->end_state));
+				DEBUG_JTAG_IO("statemove end in %s", \
+								tap_state_name(cmd->cmd.statemove->end_state));
 
 				vsllink_end_state(cmd->cmd.statemove->end_state);
 				vsllink_state_move();
@@ -280,7 +179,8 @@ static int vsllink_execute_queue(void)
 					cmd->cmd.pathmove->num_states, \
 					tap_state_name(cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]));
 
-				vsllink_path_move(cmd->cmd.pathmove->num_states, cmd->cmd.pathmove->path);
+				vsllink_path_move(cmd->cmd.pathmove->num_states, \
+									cmd->cmd.pathmove->path);
 				break;
 
 			case JTAG_SCAN:
@@ -289,24 +189,31 @@ static int vsllink_execute_queue(void)
 				scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
 				if (cmd->cmd.scan->ir_scan)
 				{
-					DEBUG_JTAG_IO("JTAG Scan write IR(%d bits), end in %s:", scan_size, tap_state_name(cmd->cmd.scan->end_state));
+					DEBUG_JTAG_IO("JTAG Scan write IR(%d bits), end in %s:", \
+									scan_size, \
+									tap_state_name(cmd->cmd.scan->end_state));
 				}
 				else
 				{
-					DEBUG_JTAG_IO("JTAG Scan write DR(%d bits), end in %s:", scan_size, tap_state_name(cmd->cmd.scan->end_state));
+					DEBUG_JTAG_IO("JTAG Scan write DR(%d bits), end in %s:", \
+									scan_size, \
+									tap_state_name(cmd->cmd.scan->end_state));
 				}
 
 #ifdef _DEBUG_JTAG_IO_
-				vsllink_debug_buffer(buffer, (scan_size + 7) >> 3);
+				vsllink_debug_buffer(buffer, DIV_ROUND_UP(scan_size, 8));
 #endif
 
 				type = jtag_scan_type(cmd->cmd.scan);
 
-				vsllink_scan(cmd->cmd.scan->ir_scan, type, buffer, scan_size, cmd->cmd.scan);
+				vsllink_scan(cmd->cmd.scan->ir_scan, type, buffer, \
+								scan_size, cmd->cmd.scan);
 				break;
 
 			case JTAG_RESET:
-				DEBUG_JTAG_IO("reset trst: %i srst %i", cmd->cmd.reset->trst, cmd->cmd.reset->srst);
+				DEBUG_JTAG_IO("reset trst: %i srst %i", \
+								cmd->cmd.reset->trst, \
+								cmd->cmd.reset->srst);
 
 				vsllink_tap_execute();
 
@@ -324,7 +231,8 @@ static int vsllink_execute_queue(void)
 				break;
 
 			case JTAG_STABLECLOCKS:
-				DEBUG_JTAG_IO("add %d clocks", cmd->cmd.stableclocks->num_cycles);
+				DEBUG_JTAG_IO("add %d clocks", \
+								cmd->cmd.stableclocks->num_cycles);
 				switch (tap_get_state())
 				{
 				case TAP_RESET:
@@ -340,15 +248,17 @@ static int vsllink_execute_queue(void)
 					scan_size = 0;
 					break;			/* above stable states are OK */
 				default:
-					 LOG_ERROR("jtag_add_clocks() was called with TAP in non-stable state \"%s\"",
-							 tap_state_name(tap_get_state()));
+					 LOG_ERROR("jtag_add_clocks() in non-stable state \"%s\"",
+								tap_state_name(tap_get_state()));
 					 exit(-1);
 				}
-				vsllink_stableclocks(cmd->cmd.stableclocks->num_cycles, scan_size);
+				vsllink_stableclocks(cmd->cmd.stableclocks->num_cycles, \
+										scan_size);
 				break;
 
 			default:
-				LOG_ERROR("BUG: unknown JTAG command type encountered: %d", cmd->type);
+				LOG_ERROR("BUG: unknown JTAG command type encountered: %d", \
+							cmd->type);
 				exit(-1);
 		}
 		cmd = cmd->next;
@@ -400,8 +310,8 @@ static int vsllink_init(void)
 	int result;
 	char version_str[100];
 
-	vsllink_usb_in_buffer = malloc(VSLLINK_BufferSize);
-	vsllink_usb_out_buffer = malloc(VSLLINK_BufferSize);
+	vsllink_usb_in_buffer = malloc(vsllink_buffer_size);
+	vsllink_usb_out_buffer = malloc(vsllink_buffer_size);
 	if ((vsllink_usb_in_buffer == NULL) || (vsllink_usb_out_buffer == NULL))
 	{
 		LOG_ERROR("Not enough memory");
@@ -409,10 +319,10 @@ static int vsllink_init(void)
 	}
 
 	vsllink_handle = vsllink_usb_open();
-
 	if (vsllink_handle == 0)
 	{
-		LOG_ERROR("Can't find USB JTAG Interface! Please check connection and permissions.");
+		LOG_ERROR("Can't find USB JTAG Interface!"\
+					"Please check connection and permissions.");
 		return ERROR_JTAG_INIT_FAILED;
 	}
 	LOG_DEBUG("vsllink found on %04X:%04X", vsllink_usb_vid, vsllink_usb_pid);
@@ -422,14 +332,16 @@ static int vsllink_init(void)
 	check_cnt = 0;
 	while (check_cnt < 5)
 	{
-		vsllink_simple_command(0x00);
+		vsllink_simple_command(VERSALOON_GET_INFO);
 		result = vsllink_usb_read(vsllink_handle);
 
 		if (result > 2)
 		{
 			vsllink_usb_in_buffer[result] = 0;
-			VSLLINK_BufferSize = vsllink_usb_in_buffer[0] + (vsllink_usb_in_buffer[1] << 8);
-			strncpy(version_str, (char *)vsllink_usb_in_buffer + 2, sizeof(version_str));
+			vsllink_buffer_size = vsllink_usb_in_buffer[0] + \
+									(vsllink_usb_in_buffer[1] << 8);
+			strncpy(version_str, (char *)vsllink_usb_in_buffer + 2, \
+					sizeof(version_str));
 			LOG_INFO("%s", version_str);
 
 			// free the pre-alloc memroy
@@ -439,29 +351,29 @@ static int vsllink_init(void)
 			vsllink_usb_out_buffer = NULL;
 
 			// alloc new memory
-			vsllink_usb_in_buffer = malloc(VSLLINK_BufferSize);
-			vsllink_usb_out_buffer = malloc(VSLLINK_BufferSize);
-			if ((vsllink_usb_in_buffer == NULL) || (vsllink_usb_out_buffer == NULL))
+			vsllink_usb_in_buffer = malloc(vsllink_buffer_size);
+			vsllink_usb_out_buffer = malloc(vsllink_buffer_size);
+			if ((vsllink_usb_in_buffer == NULL) || \
+				(vsllink_usb_out_buffer == NULL))
 			{
 				LOG_ERROR("Not enough memory");
 				exit(-1);
 			}
 			else
 			{
-				LOG_INFO("buffer size for USB is %d bytes", VSLLINK_BufferSize);
+				LOG_INFO("buffer size for USB is %d bytes", \
+							vsllink_buffer_size);
 			}
-			// alloc memory for dma mode
-			if (vsllink_mode == VSLLINK_MODE_DMA)
+			// alloc tms/tdi/tdo buffer
+			tap_buffer_size = (vsllink_buffer_size - 3) / 2;
+			tms_buffer = (uint8_t*)malloc(tap_buffer_size);
+			tdi_buffer = (uint8_t*)malloc(tap_buffer_size);
+			tdo_buffer = (uint8_t*)malloc(tap_buffer_size);
+			if ((tms_buffer == NULL) || (tdi_buffer == NULL) || \
+				(tdo_buffer == NULL))
 			{
-				tap_buffer_size = (VSLLINK_BufferSize - 3) / 2;
-				tms_buffer = (uint8_t*)malloc(tap_buffer_size);
-				tdi_buffer = (uint8_t*)malloc(tap_buffer_size);
-				tdo_buffer = (uint8_t*)malloc(tap_buffer_size);
-				if ((tms_buffer == NULL) || (tdi_buffer == NULL) || (tdo_buffer == NULL))
-				{
-					LOG_ERROR("Not enough memory");
-					exit(-1);
-				}
+				LOG_ERROR("Not enough memory");
+				exit(-1);
 			}
 			break;
 		}
@@ -470,7 +382,7 @@ static int vsllink_init(void)
 	}
 	if (check_cnt == 3)
 	{
-		// It's dangerout to proced
+		// Fail to access Versaloon
 		LOG_ERROR("VSLLink initial failed");
 		exit(-1);
 	}
@@ -479,49 +391,33 @@ static int vsllink_init(void)
 	/* Some older firmware versions sometimes fail if the
 	 * voltage isn't read first.
 	 */
-	vsllink_simple_command(0x01);
+	vsllink_simple_command(VERSALOON_GET_TVCC);
 	result = vsllink_usb_read(vsllink_handle);
 	if (result != 2)
-		LOG_WARNING("Fail to get target voltage");
-	else
-		LOG_INFO("Target runs at %d mV", vsllink_usb_in_buffer[0]
-				+ (vsllink_usb_in_buffer[1] << 8));
-
-	// connect to vsllink
-	vsllink_connect();
-	// initialize function pointers
-	if (vsllink_mode == VSLLINK_MODE_NORMAL)
 	{
-		// normal mode
-		vsllink_state_move = vsllink_state_move_normal;
-		vsllink_path_move = vsllink_path_move_normal;
-		vsllink_stableclocks = vsllink_stableclocks_normal;
-		vsllink_scan = vsllink_scan_normal;
-
-		vsllink_tap_init = vsllink_tap_init_normal;
-		vsllink_tap_execute = vsllink_tap_execute_normal;
-		vsllink_tap_ensure_space = vsllink_tap_ensure_space_normal;
-
-		LOG_INFO("vsllink run in NORMAL mode");
+		LOG_WARNING("Fail to get target voltage");
 	}
 	else
 	{
-		// dma mode
-		vsllink_state_move = vsllink_state_move_dma;
-		vsllink_path_move = vsllink_path_move_dma;
-		vsllink_stableclocks = vsllink_stableclocks_dma;
-		vsllink_scan = vsllink_scan_dma;
-
-		vsllink_tap_init = vsllink_tap_init_dma;
-		vsllink_tap_execute = vsllink_tap_execute_dma;
-		vsllink_tap_ensure_space = vsllink_tap_ensure_space_dma;
+		LOG_INFO("Target runs at %d mV", vsllink_usb_in_buffer[0] + \
+					(vsllink_usb_in_buffer[1] << 8));
+	}
 
-		LOG_INFO("vsllink run in DMA mode");
+	// connect to vsllink
+	vsllink_usb_out_buffer[0] = VSLLINK_CMD_CONN;
+	vsllink_usb_out_buffer[1] = 1;
+	vsllink_usb_message(vsllink_handle, 2, 0);
+	if (vsllink_usb_read(vsllink_handle) > 2)
+	{
+		strncpy(version_str, (char *)vsllink_usb_in_buffer + 2, \
+				sizeof(version_str));
+		LOG_INFO("%s", version_str);
 	}
 
 	// Set SRST and TRST to output, Set USR1 and USR2 to input
 	vsllink_usb_out_buffer[0] = VSLLINK_CMD_SET_PORTDIR;
-	vsllink_usb_out_buffer[1] = JTAG_PINMSK_SRST | JTAG_PINMSK_TRST | JTAG_PINMSK_USR1 | JTAG_PINMSK_USR2;
+	vsllink_usb_out_buffer[1] = JTAG_PINMSK_SRST | JTAG_PINMSK_TRST | \
+								JTAG_PINMSK_USR1 | JTAG_PINMSK_USR2;
 	vsllink_usb_out_buffer[2] = JTAG_PINMSK_SRST | JTAG_PINMSK_TRST;
 	if (vsllink_usb_write(vsllink_handle, 3) != 3)
 	{
@@ -531,7 +427,7 @@ static int vsllink_init(void)
 
 	vsllink_reset(0, 0);
 
-	LOG_INFO("VSLLink JTAG Interface ready");
+	LOG_INFO("VSLLink Interface ready");
 
 	vsllink_tap_init();
 
@@ -544,7 +440,8 @@ static int vsllink_quit(void)
 	{
 		// Set all pins to input
 		vsllink_usb_out_buffer[0] = VSLLINK_CMD_SET_PORTDIR;
-		vsllink_usb_out_buffer[1] = JTAG_PINMSK_SRST | JTAG_PINMSK_TRST | JTAG_PINMSK_USR1 | JTAG_PINMSK_USR2;
+		vsllink_usb_out_buffer[1] = JTAG_PINMSK_SRST | JTAG_PINMSK_TRST | \
+									JTAG_PINMSK_USR1 | JTAG_PINMSK_USR2;
 		vsllink_usb_out_buffer[2] = 0;
 		if (vsllink_usb_write(vsllink_handle, 3) != 3)
 		{
@@ -553,7 +450,7 @@ static int vsllink_quit(void)
 		}
 
 		// disconnect
-		vsllink_disconnect();
+		vsllink_simple_command(VSLLINK_CMD_DISCONN);
 		vsllink_usb_close(vsllink_handle);
 		vsllink_handle = NULL;
 	}
@@ -574,61 +471,6 @@ static int vsllink_quit(void)
 
 /***************************************************************************/
 /* Queue command implementations */
-static int vsllink_disconnect(void)
-{
-	vsllink_simple_command(VSLLINK_CMD_DISCONN);
-	return ERROR_OK;
-}
-
-static int vsllink_connect(void)
-{
-	char vsllink_str[100];
-
-	vsllink_usb_out_buffer[0] = VSLLINK_CMD_CONN;
-	vsllink_usb_out_buffer[1] = vsllink_mode;
-	vsllink_usb_message(vsllink_handle, 2, 0);
-	if (vsllink_usb_read(vsllink_handle) > 2)
-	{
-		strncpy(vsllink_str, (char *)vsllink_usb_in_buffer + 2, sizeof(vsllink_str));
-		LOG_INFO("%s", vsllink_str);
-	}
-
-	return ERROR_OK;
-}
-
-// when vsllink_tms_data_len > 0, vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] is the byte that need to be appended.
-// length of VSLLINK_CMDJTAGSEQ_TMSBYTE has been set, no need to set it here.
-static void vsllink_append_tms(void)
-{
-	uint8_t tms_scan = VSLLINK_TAP_MOVE(tap_get_state(), tap_get_end_state());
-	uint16_t tms2;
-	struct insert_insignificant_operation *insert = \
-		&VSLLINK_TAP_MOVE_INSERT_INSIGNIFICANT[tap_move_ndx(tap_get_state())][tap_move_ndx(tap_get_end_state())];
-
-	if (((tap_get_state() != TAP_RESET) && (tap_get_state() != TAP_IDLE) && (tap_get_state() != TAP_DRPAUSE) && (tap_get_state() != TAP_IRPAUSE)) || \
-			(vsllink_tms_data_len <= 0) || (vsllink_tms_data_len >= 8) || \
-			(vsllink_tms_cmd_pos == NULL))
-	{
-		LOG_ERROR("There MUST be some bugs in the driver");
-		exit(-1);
-	}
-
-	tms2 = (tms_scan & VSLLINK_BIT_MSK[insert->insert_position]) << \
-				vsllink_tms_data_len;
-	if (insert->insert_value == 1)
-	{
-		tms2 |= VSLLINK_BIT_MSK[8 - vsllink_tms_data_len] << \
-				(vsllink_tms_data_len + insert->insert_position);
-	}
-	tms2 |= (tms_scan >> insert->insert_position) << \
-				(8 + insert->insert_position);
-
-	vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] |= (tms2 >> 0) & 0xff;
-	vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (tms2 >> 8) & 0xff;
-
-	vsllink_tms_data_len = 0;
-	vsllink_tms_cmd_pos = NULL;
-}
 
 static void vsllink_end_state(tap_state_t state)
 {
@@ -644,482 +486,53 @@ static void vsllink_end_state(tap_state_t state)
 }
 
 /* Goes to the end state. */
-static void vsllink_state_move_normal(void)
+static void vsllink_state_move(void)
 {
-	if (vsllink_tms_data_len > 0)
-	{
-		vsllink_append_tms();
-	}
-	else
-	{
-		vsllink_tap_ensure_space(0, 2);
-
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_TMSBYTE;
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_TAP_MOVE(tap_get_state(), tap_get_end_state());
-	}
-
-	tap_set_state(tap_get_end_state());
-}
-static void vsllink_state_move_dma(void)
-{
-	int i, insert_length = (tap_length % 8) ? (8 - (tap_length % 8)) : 0;
-	struct insert_insignificant_operation *insert = \
-		&VSLLINK_TAP_MOVE_INSERT_INSIGNIFICANT[tap_move_ndx(tap_get_state())][tap_move_ndx(tap_get_end_state())];
-	uint8_t tms_scan = VSLLINK_TAP_MOVE(tap_get_state(), tap_get_end_state());
-
-	if (tap_get_state() == TAP_RESET)
-	{
-		vsllink_tap_ensure_space(0, 8);
-
-		for (i = 0; i < 8; i++)
-		{
-			vsllink_tap_append_step(1, 0);
-		}
-	}
-
-	if (insert_length > 0)
-	{
-		vsllink_tap_ensure_space(0, 16);
+	int i;
+	uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
+	uint8_t tms_scan_bits = \
+				tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
 
-		for (i = 0; i < insert->insert_position; i++)
-		{
-			vsllink_tap_append_step((tms_scan >> i) & 1, 0);
-		}
-		for (i = 0; i < insert_length; i++)
-		{
-			vsllink_tap_append_step(insert->insert_value, 0);
-		}
-		for (i = insert->insert_position; i < 8; i++)
-		{
-			vsllink_tap_append_step((tms_scan >> i) & 1, 0);
-		}
-	}
-	else
+	for (i = 0; i < tms_scan_bits; i++)
 	{
-		vsllink_tap_ensure_space(0, 8);
-
-		for (i = 0; i < 8; i++)
-		{
-			vsllink_tap_append_step((tms_scan >> i) & 1, 0);
-		}
+		vsllink_tap_append_step((tms_scan >> i) & 1, 0);
 	}
 
 	tap_set_state(tap_get_end_state());
 }
 
-// write tms from current vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx]
-static void vsllink_add_path(int start, int num, tap_state_t *path)
+static void vsllink_path_move(int num_states, tap_state_t *path)
 {
-	int i;
-
-	for (i = start; i < (start + num); i++)
+	for (int i = 0; i < num_states; i++)
 	{
-		if ((i & 7) == 0)
-		{
-			if (i > 0)
-			{
-				vsllink_usb_out_buffer_idx++;
-			}
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] = 0;
-		}
-
-		if (path[i - start] == tap_state_transition(tap_get_state(), true))
+		if (path[i] == tap_state_transition(tap_get_state(), false))
 		{
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] |= 1 << (i & 7);
+			vsllink_tap_append_step(0, 0);
 		}
-		else if (path[i - start] == tap_state_transition(tap_get_state(), false))
+		else if (path[i] == tap_state_transition(tap_get_state(), true))
 		{
-			// nothing to do
+			vsllink_tap_append_step(1, 0);
 		}
 		else
 		{
-			LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition", tap_state_name(tap_get_state()), tap_state_name(path[i]));
+			LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition", \
+						tap_state_name(tap_get_state()), \
+						tap_state_name(path[i]));
 			exit(-1);
 		}
-		tap_set_state(path[i - start]);
-	}
-	if ((i > 0) && ((i & 7) == 0))
-	{
-		vsllink_usb_out_buffer_idx++;
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] = 0;
-	}
 
-	tap_set_end_state(tap_get_state());
-}
-
-static void vsllink_path_move_normal(int num_states, tap_state_t *path)
-{
-	int i, tms_len, tms_cmd_pos, path_idx = 0;
-
-	if (vsllink_tms_data_len > 0)
-	{
-		// there are vsllink_tms_data_len more tms bits to be shifted
-		// so there are vsllink_tms_data_len + num_states tms bits in all
-		tms_len = vsllink_tms_data_len + num_states;
-		if (tms_len <= 16)
-		{
-			// merge into last tms shift
-			if (tms_len < 8)
-			{
-				// just append tms data to the last tms byte
-				vsllink_add_path(vsllink_tms_data_len, num_states, path);
-			}
-			else if (tms_len == 8)
-			{
-				// end last tms shift command
-				(*vsllink_tms_cmd_pos)--;
-				vsllink_add_path(vsllink_tms_data_len, num_states, path);
-			}
-			else if (tms_len < 16)
-			{
-				if ((*vsllink_tms_cmd_pos & VSLLINK_CMDJTAGSEQ_LENMSK) < VSLLINK_CMDJTAGSEQ_LENMSK)
-				{
-					// every tms shift command can contain VSLLINK_CMDJTAGSEQ_LENMSK + 1 bytes in most
-					// there is enought tms length in the current tms shift command
-					(*vsllink_tms_cmd_pos)++;
-					vsllink_add_path(vsllink_tms_data_len, num_states, path);
-				}
-				else
-				{
-					// every tms shift command can contain VSLLINK_CMDJTAGSEQ_LENMSK + 1 bytes in most
-					// not enough tms length in the current tms shift command
-					// so a new command should be added
-					// first decrease byte length of last tms shift command
-					(*vsllink_tms_cmd_pos)--;
-					// append tms data to the last tms byte
-					vsllink_add_path(vsllink_tms_data_len, 8 - vsllink_tms_data_len, path);
-					path += 8 - vsllink_tms_data_len;
-					// add new command(3 bytes)
-					vsllink_tap_ensure_space(0, 3);
-					vsllink_tms_cmd_pos = &vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx];
-					vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_TMSBYTE | 1;
-					vsllink_add_path(0, num_states - (8 - vsllink_tms_data_len), path);
-				}
-			}
-			else if (tms_len == 16)
-			{
-				// end last tms shift command
-				vsllink_add_path(vsllink_tms_data_len, num_states, path);
-			}
-
-			vsllink_tms_data_len = (vsllink_tms_data_len + num_states) & 7;
-			if (vsllink_tms_data_len == 0)
-			{
-				vsllink_tms_cmd_pos = NULL;
-			}
-			num_states = 0;
-		}
-		else
-		{
-			vsllink_add_path(vsllink_tms_data_len, 16 - vsllink_tms_data_len, path);
-
-			path += 16 - vsllink_tms_data_len;
-			num_states -= 16 - vsllink_tms_data_len;
-			vsllink_tms_data_len = 0;
-			vsllink_tms_cmd_pos = NULL;
-		}
-	}
-
-	if (num_states > 0)
-	{
-		// Normal operation, don't need to append tms data
-		vsllink_tms_data_len = num_states & 7;
-
-		while (num_states > 0)
-		{
-			if (num_states > ((VSLLINK_CMDJTAGSEQ_LENMSK + 1) * 8))
-			{
-				i = (VSLLINK_CMDJTAGSEQ_LENMSK + 1) * 8;
-			}
-			else
-			{
-				i = num_states;
-			}
-			tms_len = (i + 7) >> 3;
-			vsllink_tap_ensure_space(0, tms_len + 2);
-			tms_cmd_pos = vsllink_usb_out_buffer_idx;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_TMSBYTE | (tms_len - 1);
-
-			vsllink_add_path(0, i, path + path_idx);
-
-			path_idx += i;
-			num_states -= i;
-		}
-
-		if (vsllink_tms_data_len > 0)
-		{
-			if (tms_len < (VSLLINK_CMDJTAGSEQ_LENMSK + 1))
-			{
-				vsllink_tms_cmd_pos = &vsllink_usb_out_buffer[tms_cmd_pos];
-				(*vsllink_tms_cmd_pos)++;
-			}
-			else
-			{
-				vsllink_usb_out_buffer[tms_cmd_pos]--;
-
-				tms_len = vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx];
-				vsllink_tap_ensure_space(0, 3);
-				vsllink_tms_cmd_pos = &vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx];
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_TMSBYTE | 1;
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] = tms_len;
-			}
-		}
-	}
-}
-static void vsllink_path_move_dma(int num_states, tap_state_t *path)
-{
-	int i, j = 0;
-
-	if (tap_length & 7)
-	{
-		if ((8 - (tap_length & 7)) < num_states)
-		{
-			j = 8 - (tap_length & 7);
-		}
-		else
-		{
-			j = num_states;
-		}
-		for (i = 0; i < j; i++)
-		{
-			if (path[i] == tap_state_transition(tap_get_state(), false))
-			{
-				vsllink_tap_append_step(0, 0);
-			}
-			else if (path[i] == tap_state_transition(tap_get_state(), true))
-			{
-				vsllink_tap_append_step(1, 0);
-			}
-			else
-			{
-				LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition", tap_state_name(tap_get_state()), tap_state_name(path[i]));
-				exit(-1);
-			}
-			tap_set_state(path[i]);
-		}
-		num_states -= j;
-	}
-
-	if (num_states > 0)
-	{
-		vsllink_tap_ensure_space(0, num_states);
-
-		for (i = 0; i < num_states; i++)
-		{
-			if (path[j + i] == tap_state_transition(tap_get_state(), false))
-			{
-				vsllink_tap_append_step(0, 0);
-			}
-			else if (path[j + i] == tap_state_transition(tap_get_state(), true))
-			{
-				vsllink_tap_append_step(1, 0);
-			}
-			else
-			{
-				LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition", tap_state_name(tap_get_state()), tap_state_name(path[i]));
-				exit(-1);
-			}
-			tap_set_state(path[j + i]);
-		}
+		tap_set_state(path[i]);
 	}
 
 	tap_set_end_state(tap_get_state());
 }
 
-static void vsllink_stableclocks_normal(int num_cycles, int tms)
+static void vsllink_stableclocks(int num_cycles, int tms)
 {
-	int tms_len;
-	uint16_t tms_append_byte;
-
-	if (vsllink_tms_data_len > 0)
-	{
-		// there are vsllink_tms_data_len more tms bits to be shifted
-		// so there are vsllink_tms_data_len + num_cycles tms bits in all
-		tms_len = vsllink_tms_data_len + num_cycles;
-		if (tms > 0)
-		{
-			// append '1' for tms
-			tms_append_byte = (uint16_t)((((1 << num_cycles) - 1) << vsllink_tms_data_len) & 0xFFFF);
-		}
-		else
-		{
-			// append '0' for tms
-			tms_append_byte = 0;
-		}
-		if (tms_len <= 16)
-		{
-			// merge into last tms shift
-			if (tms_len < 8)
-			{
-				// just add to vsllink_tms_data_len
-				// same result if tun through
-				//vsllink_tms_data_len += num_cycles;
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] |= (uint8_t)(tms_append_byte & 0xFF);
-			}
-			else if (tms_len == 8)
-			{
-				// end last tms shift command
-				// just reduce it, and append last tms byte
-				(*vsllink_tms_cmd_pos)--;
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] |= (uint8_t)(tms_append_byte & 0xFF);
-			}
-			else if (tms_len < 16)
-			{
-				if ((*vsllink_tms_cmd_pos & VSLLINK_CMDJTAGSEQ_LENMSK) < VSLLINK_CMDJTAGSEQ_LENMSK)
-				{
-					// every tms shift command can contain VSLLINK_CMDJTAGSEQ_LENMSK + 1 bytes in most
-					// there is enought tms length in the current tms shift command
-					// increase the tms byte length by 1 and set the last byte to 0
-					(*vsllink_tms_cmd_pos)++;
-					vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] |= (uint8_t)(tms_append_byte & 0xFF);
-					vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] = (uint8_t)(tms_append_byte >> 8);
-				}
-				else
-				{
-					// every tms shift command can contain VSLLINK_CMDJTAGSEQ_LENMSK + 1 bytes in most
-					// not enough tms length in the current tms shift command
-					// so a new command should be added
-					// first decrease byte length of last tms shift command
-					(*vsllink_tms_cmd_pos)--;
-					// append last tms byte and move the command pointer to the next empty position
-					vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] |= (uint8_t)(tms_append_byte & 0xFF);
-					// add new command(3 bytes)
-					vsllink_tap_ensure_space(0, 3);
-					vsllink_tms_cmd_pos = &vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx];
-					vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_TMSBYTE | 1;
-					vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] = (uint8_t)(tms_append_byte >> 8);
-				}
-			}
-			else if (tms_len == 16)
-			{
-				// end last tms shift command
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] |= (uint8_t)(tms_append_byte & 0xFF);
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (uint8_t)(tms_append_byte >> 8);
-			}
-
-			vsllink_tms_data_len = tms_len & 7;
-			if (vsllink_tms_data_len == 0)
-			{
-				vsllink_tms_cmd_pos = NULL;
-			}
-			num_cycles = 0;
-		}
-		else
-		{
-			// more shifts will be needed
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] |= (uint8_t)(tms_append_byte & 0xFF);
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (uint8_t)(tms_append_byte >> 8);
-
-			num_cycles -= 16 - vsllink_tms_data_len;
-			vsllink_tms_data_len = 0;
-			vsllink_tms_cmd_pos = NULL;
-		}
-	}
-	// from here vsllink_tms_data_len == 0 or num_cycles == 0
-
-	if (vsllink_tms_data_len > 0)
-	{
-		// num_cycles == 0
-		// no need to shift
-		if (num_cycles > 0)
-		{
-			LOG_ERROR("There MUST be some bugs in the driver");
-			exit(-1);
-		}
-	}
-	else
-	{
-		// get number of bytes left to be sent
-		tms_len = num_cycles >> 3;
-		if (tms_len > 0)
-		{
-			vsllink_tap_ensure_space(1, 5);
-			// if tms_len > 0, vsllink_tms_data_len == 0
-			// so just add new command
-			// LSB of the command byte is the tms value when do the shifting
-			if (tms > 0)
-			{
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_TMSCLOCK | 1;
-			}
-			else
-			{
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_TMSCLOCK;
-			}
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (tms_len >> 0) & 0xff;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (tms_len >> 8) & 0xff;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (tms_len >> 16) & 0xff;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (tms_len >> 24) & 0xff;
-
-			vsllink_usb_in_want_length += 1;
-			pending_scan_results_buffer[pending_scan_results_length].buffer = NULL;
-			pending_scan_results_length++;
-
-			if (tms_len > 0xFFFF)
-			{
-				vsllink_tap_execute();
-			}
-		}
-
-		// post-process
-		vsllink_tms_data_len = num_cycles & 7;
-		if (vsllink_tms_data_len > 0)
-		{
-			vsllink_tap_ensure_space(0, 3);
-			vsllink_tms_cmd_pos = &vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx];
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_TMSBYTE | 1;
-			if (tms > 0)
-			{
-				// append '1' for tms
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] = (1 << vsllink_tms_data_len) - 1;
-			}
-			else
-			{
-				// append '0' for tms
-				vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] = 0x00;
-			}
-		}
-	}
-}
-static void vsllink_stableclocks_dma(int num_cycles, int tms)
-{
-	int i, cur_cycles;
-
-	if (tap_length & 7)
-	{
-		if ((8 - (tap_length & 7)) < num_cycles)
-		{
-			cur_cycles = 8 - (tap_length & 7);
-		}
-		else
-		{
-			cur_cycles = num_cycles;
-		}
-		for (i = 0; i < cur_cycles; i++)
-		{
-			vsllink_tap_append_step(tms, 0);
-		}
-		num_cycles -= cur_cycles;
-	}
-
 	while (num_cycles > 0)
 	{
-		if (num_cycles > 8 * tap_buffer_size)
-		{
-			cur_cycles = 8 * tap_buffer_size;
-		}
-		else
-		{
-			cur_cycles = num_cycles;
-		}
-
-		vsllink_tap_ensure_space(0, cur_cycles);
-
-		for (i = 0; i < cur_cycles; i++)
-		{
-			vsllink_tap_append_step(tms, 0);
-		}
-
-		num_cycles -= cur_cycles;
+		vsllink_tap_append_step(tms, 0);
+		num_cycles--;
 	}
 }
 
@@ -1139,150 +552,36 @@ static void vsllink_runtest(int num_cycles)
 	// post-process
 	// set end_state
 	vsllink_end_state(saved_end_state);
-	tap_set_state(TAP_IDLE);
-	if (tap_get_end_state() != TAP_IDLE)
+	if (tap_get_end_state() != tap_get_end_state())
 	{
 		vsllink_state_move();
 	}
 }
 
-static void vsllink_scan_normal(bool ir_scan, enum scan_type type, uint8_t *buffer, int scan_size, struct scan_command *command)
+static void vsllink_scan(bool ir_scan, enum scan_type type, uint8_t *buffer, \
+							int scan_size, struct scan_command *command)
 {
 	tap_state_t saved_end_state;
-	uint8_t bits_left, tms_tmp, tdi_len;
-	int i;
-
-	if (0 == scan_size)
-	{
-		return;
-	}
-
-	tdi_len = ((scan_size + 7) >> 3);
-	if ((tdi_len + 7) > VSLLINK_BufferSize)
-	{
-		LOG_ERROR("Your implementation of VSLLink has not enough buffer");
-		exit(-1);
-	}
 
 	saved_end_state = tap_get_end_state();
 
 	/* Move to appropriate scan state */
 	vsllink_end_state(ir_scan ? TAP_IRSHIFT : TAP_DRSHIFT);
 
-	if (vsllink_tms_data_len > 0)
-	{
-		if (tap_get_state() == tap_get_end_state())
-		{
-			// already in IRSHIFT or DRSHIFT state
-			// merge tms data in the last tms shift command into next scan command
-			if (*vsllink_tms_cmd_pos < 1)
-			{
-				LOG_ERROR("There MUST be some bugs in the driver");
-				exit(-1);
-			}
-			else if (*vsllink_tms_cmd_pos < 2)
-			{
-				tms_tmp = vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx];
-				vsllink_usb_out_buffer_idx--;
-			}
-			else
-			{
-				tms_tmp = vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx];
-				*vsllink_tms_cmd_pos -= 2;
-			}
-
-			vsllink_tap_ensure_space(1, tdi_len + 7);
-			// VSLLINK_CMDJTAGSEQ_SCAN ored by 1 means that tms_before is valid
-			// which is merged from the last tms shift command
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_SCAN | 1;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = ((tdi_len + 1) >> 0) & 0xff;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = ((tdi_len + 1) >> 8) & 0xff;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = tms_tmp;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = buffer[0] << (8 - vsllink_tms_data_len);
-
-			for (i = 0; i < tdi_len; i++)
-			{
-				buffer[i] >>= 8 - vsllink_tms_data_len;
-				if (i != tdi_len)
-				{
-					buffer[i] += buffer[i + 1] << vsllink_tms_data_len;
-				}
-			}
-
-			vsllink_tap_append_scan_normal(scan_size - vsllink_tms_data_len, buffer, command, vsllink_tms_data_len);
-			scan_size -= 8 - vsllink_tms_data_len;
-			vsllink_tms_data_len = 0;
-		}
-		else
-		{
-			vsllink_state_move();
-			vsllink_tap_ensure_space(1, tdi_len + 5);
-
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_SCAN;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (tdi_len >> 0) & 0xff;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = (tdi_len >> 8) & 0xff;
-
-			vsllink_tap_append_scan_normal(scan_size, buffer, command, 0);
-		}
-	}
-	else
-	{
-		vsllink_tap_ensure_space(1, tdi_len + 7);
-
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_CMDJTAGSEQ_SCAN | 1;
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = ((tdi_len + 1) >> 0) & 0xff;
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = ((tdi_len + 1)>> 8) & 0xff;
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_TAP_MOVE(tap_get_state(), tap_get_end_state());
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = 0;
-
-		vsllink_tap_append_scan_normal(scan_size, buffer, command, 8);
-	}
-	vsllink_end_state(saved_end_state);
-
-	bits_left = scan_size & 0x07;
-	tap_set_state(ir_scan ? TAP_IRPAUSE : TAP_DRPAUSE);
-
-	if (bits_left > 0)
-	{
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = 1 << (bits_left - 1);
-	}
-	else
-	{
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = 1 << 7;
-	}
-
 	if (tap_get_state() != tap_get_end_state())
 	{
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = VSLLINK_TAP_MOVE(tap_get_state(), tap_get_end_state());
-	}
-	else
-	{
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = 0;
+		vsllink_state_move();
 	}
-
-	tap_set_state(tap_get_end_state());
-}
-static void vsllink_scan_dma(bool ir_scan, enum scan_type type, uint8_t *buffer, int scan_size, struct scan_command *command)
-{
-	tap_state_t saved_end_state;
-
-	saved_end_state = tap_get_end_state();
-
-	/* Move to appropriate scan state */
-	vsllink_end_state(ir_scan ? TAP_IRSHIFT : TAP_DRSHIFT);
-
-	vsllink_state_move();
 	vsllink_end_state(saved_end_state);
 
 	/* Scan */
-	vsllink_tap_append_scan_dma(scan_size, buffer, command);
+	vsllink_tap_append_scan(scan_size, buffer, command);
+
+	/* Goto Pause and record position to insert tms:0 */
+	vsllink_tap_append_step(0, 0);
+	vsllink_tms_offset = tap_length;
 
 	tap_set_state(ir_scan ? TAP_IRPAUSE : TAP_DRPAUSE);
-	while (tap_length % 8 != 0)
-	{
-		// more 0s in Pause
-		vsllink_tap_append_step(0, 0);
-	}
 
 	if (tap_get_state() != tap_get_end_state())
 	{
@@ -1334,21 +633,8 @@ static void vsllink_simple_command(uint8_t command)
 COMMAND_HANDLER(vsllink_handle_mode_command)
 {
 	if (CMD_ARGC != 1) {
-		LOG_ERROR("parameter error, should be one parameter for VID");
-		return ERROR_FAIL;
-	}
-
-	if (!strcmp(CMD_ARGV[0], "normal"))
-	{
-		vsllink_mode = VSLLINK_MODE_NORMAL;
-	}
-	else if (!strcmp(CMD_ARGV[0], "dma"))
-	{
-		vsllink_mode = VSLLINK_MODE_DMA;
-	}
-	else
-	{
-		LOG_ERROR("invalid vsllink_mode: %s", CMD_ARGV[0]);
+		LOG_ERROR("parameter error, "
+					"should be one parameter for mode");
 		return ERROR_FAIL;
 	}
 
@@ -1359,7 +645,8 @@ COMMAND_HANDLER(vsllink_handle_usb_vid_command)
 {
 	if (CMD_ARGC != 1)
 	{
-		LOG_ERROR("parameter error, should be one parameter for VID");
+		LOG_ERROR("parameter error, "
+					"should be one parameter for VID");
 		return ERROR_OK;
 	}
 
@@ -1371,7 +658,8 @@ COMMAND_HANDLER(vsllink_handle_usb_pid_command)
 {
 	if (CMD_ARGC != 1)
 	{
-		LOG_ERROR("parameter error, should be one parameter for PID");
+		LOG_ERROR("parameter error, "
+					"should be one parameter for PID");
 		return ERROR_OK;
 	}
 	COMMAND_PARSE_NUMBER(u16, CMD_ARGV[0], vsllink_usb_pid);
@@ -1382,7 +670,8 @@ COMMAND_HANDLER(vsllink_handle_usb_bulkin_command)
 {
 	if (CMD_ARGC != 1)
 	{
-		LOG_ERROR("parameter error, should be one parameter for BULKIN endpoint");
+		LOG_ERROR("parameter error, "
+					"should be one parameter for BULKIN endpoint");
 		return ERROR_OK;
 	}
 
@@ -1397,7 +686,8 @@ COMMAND_HANDLER(vsllink_handle_usb_bulkout_command)
 {
 	if (CMD_ARGC != 1)
 	{
-		LOG_ERROR("parameter error, should be one parameter for BULKOUT endpoint");
+		LOG_ERROR("parameter error, "
+					"should be one parameter for BULKOUT endpoint");
 		return ERROR_OK;
 	}
 
@@ -1412,7 +702,8 @@ COMMAND_HANDLER(vsllink_handle_usb_interface_command)
 {
 	if (CMD_ARGC != 1)
 	{
-		LOG_ERROR("parameter error, should be one parameter for interface number");
+		LOG_ERROR("parameter error, "
+					"should be one parameter for interface number");
 		return ERROR_OK;
 	}
 
@@ -1423,34 +714,19 @@ COMMAND_HANDLER(vsllink_handle_usb_interface_command)
 /***************************************************************************/
 /* VSLLink tap functions */
 
-static void vsllink_tap_init_normal(void)
-{
-	vsllink_usb_out_buffer_idx = 0;
-	vsllink_usb_in_want_length = 0;
-	pending_scan_results_length = 0;
-}
-static void vsllink_tap_init_dma(void)
+static void vsllink_tap_init(void)
 {
 	tap_length = 0;
 	pending_scan_results_length = 0;
+	vsllink_tms_offset = 0;
 }
 
-static void vsllink_tap_ensure_space_normal(int scans, int length)
-{
-	int available_scans = MAX_PENDING_SCAN_RESULTS - pending_scan_results_length;
-	int available_bytes = VSLLINK_BufferSize - vsllink_usb_out_buffer_idx;
-
-	if (scans > available_scans || length > available_bytes)
-	{
-		vsllink_tap_execute();
-	}
-}
-static void vsllink_tap_ensure_space_dma(int scans, int length)
+static void vsllink_tap_ensure_pending(int scans)
 {
-	int available_scans = MAX_PENDING_SCAN_RESULTS - pending_scan_results_length;
-	int available_bytes = tap_buffer_size * 8 - tap_length;
+	int available_scans = \
+			MAX_PENDING_SCAN_RESULTS - pending_scan_results_length;
 
-	if (scans > available_scans || length > available_bytes)
+	if (scans > available_scans)
 	{
 		vsllink_tap_execute();
 	}
@@ -1458,66 +734,38 @@ static void vsllink_tap_ensure_space_dma(int scans, int length)
 
 static void vsllink_tap_append_step(int tms, int tdi)
 {
-	last_tms = tms;
 	int index = tap_length / 8;
 
-	if (index < tap_buffer_size)
-	{
-		int bit_index = tap_length % 8;
-		uint8_t bit = 1 << bit_index;
-
-		if (tms)
-		{
-			tms_buffer[index] |= bit;
-		}
-		else
-		{
-			tms_buffer[index] &= ~bit;
-		}
+	int bit_index = tap_length % 8;
+	uint8_t bit = 1 << bit_index;
 
-		if (tdi)
-		{
-			tdi_buffer[index] |= bit;
-		}
-		else
-		{
-			tdi_buffer[index] &= ~bit;
-		}
-
-		tap_length++;
+	if (tms)
+	{
+		tms_buffer[index] |= bit;
 	}
 	else
 	{
-		LOG_ERROR("buffer overflow, tap_length=%d", tap_length);
+		tms_buffer[index] &= ~bit;
 	}
-}
 
-static void vsllink_tap_append_scan_normal(int length, uint8_t *buffer, struct scan_command *command, int offset)
-{
-	struct pending_scan_result *pending_scan_result = &pending_scan_results_buffer[pending_scan_results_length];
-	int i;
-
-	if (offset > 0)
+	if (tdi)
 	{
-		vsllink_usb_in_want_length += ((length + 7) >> 3) + 1;
+		tdi_buffer[index] |= bit;
 	}
 	else
 	{
-		vsllink_usb_in_want_length += (length + 7) >> 3;
+		tdi_buffer[index] &= ~bit;
 	}
-	pending_scan_result->length = length;
-	pending_scan_result->offset = offset;
-	pending_scan_result->command = command;
-	pending_scan_result->buffer = buffer;
 
-	for (i = 0; i < ((length + 7) >> 3); i++)
+	tap_length++;
+	if (tap_buffer_size * 8 <= tap_length)
 	{
-		vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = buffer[i];
+		vsllink_tap_execute();
 	}
-
-	pending_scan_results_length++;
 }
-static void vsllink_tap_append_scan_dma(int length, uint8_t *buffer, struct scan_command *command)
+
+static void vsllink_tap_append_scan(int length, uint8_t *buffer, \
+										struct scan_command *command)
 {
 	struct pending_scan_result *pending_scan_result;
 	int len_tmp, len_all, i;
@@ -1525,164 +773,140 @@ static void vsllink_tap_append_scan_dma(int length, uint8_t *buffer, struct scan
 	len_all = 0;
 	while (len_all < length)
 	{
-		if ((length - len_all) > tap_buffer_size * 8)
+		vsllink_tap_ensure_pending(1);
+		pending_scan_result = \
+				&pending_scan_results_buffer[pending_scan_results_length];
+
+		if ((length - len_all) > (tap_buffer_size * 8 - tap_length))
 		{
-			len_tmp = tap_buffer_size * 8;
+			/* Use all memory available 
+			   vsllink_tap_append_step will commit automatically */
+			len_tmp = tap_buffer_size * 8 - tap_length;
+			pending_scan_result->last = false;
 		}
 		else
 		{
 			len_tmp = length - len_all;
+			pending_scan_result->last = true;
 		}
-
-		vsllink_tap_ensure_space(1, (len_tmp + 7) & ~7);
-
-		pending_scan_result = &pending_scan_results_buffer[pending_scan_results_length];
-		pending_scan_result->offset = tap_length;
+		pending_scan_result->src_offset = tap_length;
+		pending_scan_result->dest_offset = len_all;
 		pending_scan_result->length = len_tmp;
 		pending_scan_result->command = command;
-		pending_scan_result->buffer = buffer + len_all / 8;
+		pending_scan_result->buffer = buffer;
+		pending_scan_results_length++;
 
 		for (i = 0; i < len_tmp; i++)
 		{
-			vsllink_tap_append_step(((len_all + i) < length-1 ? 0 : 1), (buffer[(len_all + i)/8] >> ((len_all + i)%8)) & 1);
+			vsllink_tap_append_step(((len_all + i) < length-1 ? 0 : 1), \
+						(buffer[(len_all + i)/8] >> ((len_all + i)%8)) & 1);
 		}
 
-		pending_scan_results_length++;
 		len_all += len_tmp;
 	}
 }
 
-/* Pad and send a tap sequence to the device, and receive the answer.
- * For the purpose of padding we assume that we are in reset or idle or pause state. */
-static int vsllink_tap_execute_normal(void)
+static int vsllink_tap_execute(void)
 {
+	int byte_length;
 	int i;
 	int result;
-	int first = 0;
 
-	if (vsllink_tms_data_len > 0)
+	if (tap_length <= 0)
 	{
-		if ((tap_get_state() != TAP_RESET) && (tap_get_state() != TAP_IDLE) && (tap_get_state() != TAP_IRPAUSE) && (tap_get_state() != TAP_DRPAUSE))
-		{
-			LOG_WARNING("%s is not in RESET or IDLE or PAUSR state", tap_state_name(tap_get_state()));
-		}
-
-		if (vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx] & (1 << (vsllink_tms_data_len - 1)))
-		{
-			// last tms bit is '1'
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] |= 0xFF << vsllink_tms_data_len;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = 0xFF;
-			vsllink_tms_data_len = 0;
-		}
-		else
-		{
-			// last tms bit is '0'
-			vsllink_usb_out_buffer_idx++;
-			vsllink_usb_out_buffer[vsllink_usb_out_buffer_idx++] = 0;
-			vsllink_tms_data_len = 0;
-		}
+		return ERROR_OK;
 	}
 
-	if (vsllink_usb_out_buffer_idx > 3)
+	/* Pad data so that tap_length is divisible by 8 */
+	if ((tap_length % 8) != 0)
 	{
-		if (vsllink_usb_out_buffer[0] == VSLLINK_CMD_HW_JTAGSEQCMD)
+		if (vsllink_tms_offset > 0)
 		{
-			vsllink_usb_out_buffer[1] = (vsllink_usb_out_buffer_idx >> 0) & 0xff;
-			vsllink_usb_out_buffer[2] = (vsllink_usb_out_buffer_idx >> 8) & 0xff;
-		}
+			/* append tms:0 at vsllink_tms_offset, which is in Pause */
+			int start_pos = DIV_ROUND_UP(tap_length, 8) - 1;
+			int end_pos = DIV_ROUND_UP(vsllink_tms_offset, 8) - 1;
+			int shift_cnt = (start_pos + 1) * 8 - tap_length;
+			uint8_t last_mask = ~((1 << (vsllink_tms_offset % 8)) - 1);
 
-		result = vsllink_usb_message(vsllink_handle, vsllink_usb_out_buffer_idx, vsllink_usb_in_want_length);
-
-		if (result == vsllink_usb_in_want_length)
-		{
-			for (i = 0; i < pending_scan_results_length; i++)
+			while (1)
 			{
-				struct pending_scan_result *pending_scan_result = &pending_scan_results_buffer[i];
-				uint8_t *buffer = pending_scan_result->buffer;
-				int length = pending_scan_result->length;
-				int offset = pending_scan_result->offset;
-				struct scan_command *command = pending_scan_result->command;
-
-				if (buffer != NULL)
+				if (start_pos == end_pos)
 				{
-					// IRSHIFT or DRSHIFT
-					buf_set_buf(vsllink_usb_in_buffer, first * 8 + offset, buffer, 0, length);
-					first += (length + offset + 7) >> 3;
-
-					DEBUG_JTAG_IO("JTAG scan read(%d bits):", length);
-#ifdef _DEBUG_JTAG_IO_
-					vsllink_debug_buffer(buffer, (length + 7) >> 3);
-#endif
-
-					if (jtag_read_buffer(buffer, command) != ERROR_OK)
-					{
-						vsllink_tap_init();
-						return ERROR_JTAG_QUEUE_FAILED;
-					}
-
-					free(pending_scan_result->buffer);
-					pending_scan_result->buffer = NULL;
+					tms_buffer[start_pos] = \
+								(tms_buffer[start_pos] & ~last_mask) | \
+								((tms_buffer[start_pos] & last_mask) << shift_cnt);
+					tdi_buffer[start_pos] = \
+								(tdi_buffer[start_pos] & ~last_mask) | \
+								((tdi_buffer[start_pos] & last_mask) << shift_cnt);
+					break;
+				}
+				else if (start_pos == (end_pos + 1))
+				{
+					tms_buffer[start_pos] = \
+						(tms_buffer[start_pos] << shift_cnt) | \
+						((tms_buffer[start_pos - 1] & last_mask) >> (8 - shift_cnt));
+					tdi_buffer[start_pos] = \
+						(tdi_buffer[start_pos] << shift_cnt) | \
+						((tdi_buffer[start_pos - 1] & last_mask) >> (8 - shift_cnt));
 				}
 				else
 				{
-					first++;
+					tms_buffer[start_pos] = \
+						(tms_buffer[start_pos] << shift_cnt) | \
+						(tms_buffer[start_pos - 1] >> (8 - shift_cnt));
+					tdi_buffer[start_pos] = \
+						(tdi_buffer[start_pos] << shift_cnt) | \
+						(tdi_buffer[start_pos - 1] >> (8 - shift_cnt));
 				}
+				start_pos--;
 			}
+			tap_length = DIV_ROUND_UP(tap_length, 8) * 8;
 		}
 		else
 		{
-			LOG_ERROR("vsllink_tap_execute, wrong result %d, expected %d", result, vsllink_usb_in_want_length);
-			return ERROR_JTAG_QUEUE_FAILED;
+			/* append data at last */
+			while ((tap_length % 8) != 0)
+			{
+				vsllink_tap_append_step((tap_get_state() == TAP_RESET)?1:0, 0);
+			}
 		}
-
-		vsllink_tap_init();
 	}
-	reset_command_pointer();
-
-	return ERROR_OK;
-}
-static int vsllink_tap_execute_dma(void)
-{
-	int byte_length;
-	int i;
-	int result;
+	byte_length = tap_length / 8;
 
-	if (tap_length > 0)
-	{
-		/* Pad last byte so that tap_length is divisible by 8 */
-		while (tap_length % 8 != 0)
-		{
-			/* More of the last TMS value keeps us in the same state,
-			 * analogous to free-running JTAG interfaces. */
-			vsllink_tap_append_step(last_tms, 0);
-		}
-		byte_length = tap_length / 8;
+	vsllink_usb_out_buffer[0] = VSLLINK_CMD_HW_JTAGRAWCMD;
+	vsllink_usb_out_buffer[1] = ((byte_length * 2 + 3) >> 0) & 0xff;
+	vsllink_usb_out_buffer[2] = ((byte_length * 2 + 3) >> 8) & 0xff;
 
-		vsllink_usb_out_buffer[0] = VSLLINK_CMD_HW_JTAGRAWCMD;
-		vsllink_usb_out_buffer[1] = ((byte_length * 2 + 3) >> 0) & 0xff;		// package size
-		vsllink_usb_out_buffer[2] = ((byte_length * 2 + 3) >> 8) & 0xff;
+	memcpy(&vsllink_usb_out_buffer[3], tdi_buffer, byte_length);
+	memcpy(&vsllink_usb_out_buffer[3 + byte_length], tms_buffer, byte_length);
 
-		memcpy(&vsllink_usb_out_buffer[3], tdi_buffer, byte_length);
-		memcpy(&vsllink_usb_out_buffer[3 + byte_length], tms_buffer, byte_length);
+	result = vsllink_usb_message(vsllink_handle, 3 + 2 * byte_length, \
+									byte_length);
 
-		result = vsllink_usb_message(vsllink_handle, 3 + 2 * byte_length, byte_length);
-		if (result == byte_length)
+	if (result == byte_length)
+	{
+		for (i = 0; i < pending_scan_results_length; i++)
 		{
-			for (i = 0; i < pending_scan_results_length; i++)
-			{
-				struct pending_scan_result *pending_scan_result = &pending_scan_results_buffer[i];
-				uint8_t *buffer = pending_scan_result->buffer;
-				int length = pending_scan_result->length;
-				int first = pending_scan_result->offset;
-
-				struct scan_command *command = pending_scan_result->command;
-				buf_set_buf(vsllink_usb_in_buffer, first, buffer, 0, length);
-
-				DEBUG_JTAG_IO("JTAG scan read(%d bits, from %d bits):", length, first);
+			struct pending_scan_result *pending_scan_result = \
+											&pending_scan_results_buffer[i];
+			uint8_t *buffer = pending_scan_result->buffer;
+			int length = pending_scan_result->length;
+			int src_first = pending_scan_result->src_offset;
+			int dest_first = pending_scan_result->dest_offset;
+			bool last = pending_scan_result->last;
+
+			struct scan_command *command = pending_scan_result->command;
+			buf_set_buf(vsllink_usb_in_buffer, src_first, buffer, \
+							dest_first, length);
+
+			DEBUG_JTAG_IO("JTAG scan read(%d bits, from %d bits):", \
+							length, dest_first);
 #ifdef _DEBUG_JTAG_IO_
-				vsllink_debug_buffer(buffer, (length + 7) >> 3);
+			vsllink_debug_buffer(buffer + dest_first / 8, DIV_ROUND_UP(length, 7));
 #endif
 
+			if (last)
+			{
 				if (jtag_read_buffer(buffer, command) != ERROR_OK)
 				{
 					vsllink_tap_init();
@@ -1695,14 +919,15 @@ static int vsllink_tap_execute_dma(void)
 				}
 			}
 		}
-		else
-		{
-			LOG_ERROR("vsllink_tap_execute, wrong result %d, expected %d", result, byte_length);
-			return ERROR_JTAG_QUEUE_FAILED;
-		}
-
-		vsllink_tap_init();
 	}
+	else
+	{
+		LOG_ERROR("vsllink_tap_execute, wrong result %d, expected %d", \
+					result, byte_length);
+		return ERROR_JTAG_QUEUE_FAILED;
+	}
+
+	vsllink_tap_init();
 
 	return ERROR_OK;
 }
@@ -1757,7 +982,8 @@ static void vsllink_usb_close(struct vsllink *vsllink)
 	ret = usb_release_interface(vsllink->usb_handle, vsllink_usb_interface);
 	if (ret != 0)
 	{
-		LOG_ERROR("fail to release interface %d, %d returned", vsllink_usb_interface, ret);
+		LOG_ERROR("fail to release interface %d, %d returned", \
+					vsllink_usb_interface, ret);
 		exit(-1);
 	}
 
@@ -1772,7 +998,8 @@ static void vsllink_usb_close(struct vsllink *vsllink)
 }
 
 /* Send a message and receive the reply. */
-static int vsllink_usb_message(struct vsllink *vsllink, int out_length, int in_length)
+static int vsllink_usb_message(struct vsllink *vsllink, int out_length, \
+								int in_length)
 {
 	int result;
 
@@ -1788,7 +1015,8 @@ static int vsllink_usb_message(struct vsllink *vsllink, int out_length, int in_l
 			}
 			else
 			{
-				LOG_ERROR("usb_bulk_read failed (requested=%d, result=%d)", in_length, result);
+				LOG_ERROR("usb_bulk_read failed (requested=%d, result=%d)", \
+							in_length, result);
 				return -1;
 			}
 		}
@@ -1796,7 +1024,8 @@ static int vsllink_usb_message(struct vsllink *vsllink, int out_length, int in_l
 	}
 	else
 	{
-		LOG_ERROR("usb_bulk_write failed (requested=%d, result=%d)", out_length, result);
+		LOG_ERROR("usb_bulk_write failed (requested=%d, result=%d)", \
+					out_length, result);
 		return -1;
 	}
 }
@@ -1806,16 +1035,18 @@ static int vsllink_usb_write(struct vsllink *vsllink, int out_length)
 {
 	int result;
 
-	if (out_length > VSLLINK_BufferSize)
+	if (out_length > vsllink_buffer_size)
 	{
-		LOG_ERROR("vsllink_write illegal out_length=%d (max=%d)", out_length, VSLLINK_BufferSize);
+		LOG_ERROR("vsllink_write illegal out_length=%d (max=%d)", \
+					out_length, vsllink_buffer_size);
 		return -1;
 	}
 
 	result = usb_bulk_write(vsllink->usb_handle, vsllink_usb_bulkout, \
 		(char *)vsllink_usb_out_buffer, out_length, VSLLINK_USB_TIMEOUT);
 
-	DEBUG_JTAG_IO("vsllink_usb_write, out_length = %d, result = %d", out_length, result);
+	DEBUG_JTAG_IO("vsllink_usb_write, out_length = %d, result = %d", \
+					out_length, result);
 
 #ifdef _DEBUG_USB_COMMS_
 	LOG_DEBUG("USB out:");
@@ -1833,7 +1064,8 @@ static int vsllink_usb_write(struct vsllink *vsllink, int out_length)
 static int vsllink_usb_read(struct vsllink *vsllink)
 {
 	int result = usb_bulk_read(vsllink->usb_handle, vsllink_usb_bulkin, \
-		(char *)vsllink_usb_in_buffer, VSLLINK_BufferSize, VSLLINK_USB_TIMEOUT);
+		(char *)vsllink_usb_in_buffer, vsllink_buffer_size, \
+		VSLLINK_USB_TIMEOUT);
 
 	DEBUG_JTAG_IO("vsllink_usb_read, result = %d", result);