diff options
| -rw-r--r-- | doc/openocd.texi | 36 | ||||
| -rw-r--r-- | src/jtag/parport.c | 72 |
2 files changed, 100 insertions, 8 deletions
diff --git a/doc/openocd.texi b/doc/openocd.texi index 475482df..8547fda4 100644 --- a/doc/openocd.texi +++ b/doc/openocd.texi @@ -1975,6 +1975,42 @@ When using PPDEV to access the parallel port, use the number of the parallel por you may encounter a problem. @end deffn +@deffn Command {parport_toggling_time} [nanoseconds] +Displays how many nanoseconds the hardware needs to toggle TCK; +the parport driver uses this value to obey the +@command{jtag_khz} configuration. +When the optional @var{nanoseconds} parameter is given, +that setting is changed before displaying the current value. + +The default setting should work reasonably well on commodity PC hardware. +However, you may want to calibrate for your specific hardware. +@quotation Tip +To measure the toggling time with a logic analyzer or a digital storage +oscilloscope, follow the procedure below: +@example +> parport_toggling_time 1000 +> jtag_khz 500 +@end example +This sets the maximum JTAG clock speed of the hardware, but +the actual speed probably deviates from the requested 500 kHz. +Now, measure the time between the two closest spaced TCK transitions. +You can use @command{runtest 1000} or something similar to generate a +large set of samples. +Update the setting to match your measurement: +@example +> parport_toggling_time <measured nanoseconds> +@end example +Now the clock speed will be a better match for @command{jtag_khz rate} +commands given in OpenOCD scripts and event handlers. + +You can do something similar with many digital multimeters, but note +that you'll probably need to run the clock continuously for several +seconds before it decides what clock rate to show. Adjust the +toggling time up or down until the measured clock rate is a good +match for the jtag_khz rate you specified; be conservative. +@end quotation +@end deffn + @deffn {Config Command} {parport_write_on_exit} (on|off) This will configure the parallel driver to write a known cable-specific value to the parallel interface on exiting OpenOCD diff --git a/src/jtag/parport.c b/src/jtag/parport.c index fdf7df4d..9b202902 100644 --- a/src/jtag/parport.c +++ b/src/jtag/parport.c @@ -105,6 +105,8 @@ static cable_t cables[] = static char* parport_cable = NULL; static uint16_t parport_port; static int parport_exit = 0; +static uint32_t parport_toggling_time_ns = 1000; +static int wait_states; /* interface variables */ @@ -152,7 +154,7 @@ static __inline__ void parport_write_data(void) static void parport_write(int tck, int tms, int tdi) { - int i = jtag_get_speed() + 1; + int i = wait_states + 1; if (tck) dataport_value |= cable->TCK_MASK; @@ -204,6 +206,26 @@ static void parport_led(int on) static int parport_speed(int speed) { + wait_states = speed; + return ERROR_OK; +} + +static int parport_khz(int khz, int* jtag_speed) +{ + if (khz == 0) { + LOG_DEBUG("RCLK not supported"); + return ERROR_FAIL; + } + + *jtag_speed = 499999 / (khz * parport_toggling_time_ns); + return ERROR_OK; +} + +static int parport_speed_div(int speed, int* khz) +{ + uint32_t denominator = (speed + 1) * parport_toggling_time_ns; + + *khz = (499999 + denominator) / denominator; return ERROR_OK; } @@ -364,6 +386,8 @@ static int parport_init(void) bitbang_interface = &parport_bitbang; + wait_states = jtag_get_speed(); + return ERROR_OK; } @@ -438,6 +462,32 @@ static int parport_handle_write_on_exit_command(struct command_context_s *cmd_ct return ERROR_OK; } +static int +parport_handle_parport_toggling_time_command(struct command_context_s *cmd_ctx, + char *cmd, char **args, int argc) +{ + if (argc == 1) { + uint32_t ns; + int retval = parse_u32(args[0], &ns); + + if (ERROR_OK != retval) + return retval; + + if (ns == 0) { + LOG_ERROR("0 ns is not a valid parport toggling time"); + return ERROR_FAIL; + } + + parport_toggling_time_ns = ns; + wait_states = jtag_get_speed(); + } + + command_print(cmd_ctx, "parport toggling time = %" PRIu32 " ns", + parport_toggling_time_ns); + + return ERROR_OK; +} + static int parport_register_commands(struct command_context_s *cmd_ctx) { register_command(cmd_ctx, NULL, "parport_port", @@ -455,14 +505,20 @@ static int parport_register_commands(struct command_context_s *cmd_ctx) "configure the parallel driver to write " "a known value to the parallel interface"); + register_command(cmd_ctx, NULL, "parport_toggling_time", + parport_handle_parport_toggling_time_command, COMMAND_ANY, + "time <ns> it takes for the hardware to toggle TCK"); + return ERROR_OK; } jtag_interface_t parport_interface = { - .name = "parport", - .register_commands = &parport_register_commands, - .init = &parport_init, - .quit = &parport_quit, - .speed = &parport_speed, - .execute_queue = &bitbang_execute_queue, - }; + .name = "parport", + .register_commands = parport_register_commands, + .init = parport_init, + .quit = parport_quit, + .khz = parport_khz, + .speed_div = parport_speed_div, + .speed = parport_speed, + .execute_queue = bitbang_execute_queue, +}; |