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diff --git a/doc/openocd.texi b/doc/openocd.texi index 05b6f4e8..ee5c723d 100644 --- a/doc/openocd.texi +++ b/doc/openocd.texi @@ -23,7 +23,7 @@ of the Open On-Chip Debugger (OpenOCD). @item Copyright @copyright{} 2007-2008 Spencer Oliver @email{spen@@spen-soft.co.uk} @item Copyright @copyright{} 2008 Oyvind Harboe @email{oyvind.harboe@@zylin.com} @item Copyright @copyright{} 2008 Duane Ellis @email{openocd@@duaneellis.com} -@item Copyright @copyright{} 2009 David Brownell +@item Copyright @copyright{} 2009-2010 David Brownell @end itemize @quotation @@ -1027,6 +1027,86 @@ various kinds of message. @end itemize +@section Target Hardware Setup + +Chip vendors often provide software development boards which +are highly configurable, so that they can support all options +that product boards may require. @emph{Make sure that any +jumpers or switches match the system configuration you are +working with.} + +Common issues include: + +@itemize @bullet + +@item @b{JTAG setup} ... +Boards may support more than one JTAG configuration. +Examples include jumpers controlling pullups versus pulldowns +on the nTRST and/or nSRST signals, and choice of connectors +(e.g. which of two headers on the base board, +or one from a daughtercard). +For some Texas Instruments boards, you may need to jumper the +EMU0 and EMU1 signals (which OpenOCD won't currently control). + +@item @b{Boot Modes} ... +Complex chips often support multiple boot modes, controlled +by external jumpers. Make sure this is set up correctly. +For example many i.MX boards from NXP need to be jumpered +to "ATX mode" to start booting using the on-chip ROM, when +using second stage bootloader code stored in a NAND flash chip. + +Such explicit configuration is common, and not limited to +booting from NAND. You might also need to set jumpers to +start booting using code loaded from an MMC/SD card; external +SPI flash; Ethernet, UART, or USB links; NOR flash; OneNAND +flash; some external host; or various other sources. + + +@item @b{Memory Addressing} ... +Boards which support multiple boot modes may also have jumpers +to configure memory addressing. One board, for example, jumpers +external chipselect 0 (used for booting) to address either +a large SRAM (which must be pre-loaded via JTAG), NOR flash, +or NAND flash. When it's jumpered to address NAND flash, that +board must also be told to start booting from on-chip ROM. + +Your @file{board.cfg} file may also need to be told this jumper +configuration, so that it can know whether to declare NOR flash +using @command{flash bank} or instead declare NAND flash with +@command{nand device}; and likewise which probe to perform in +its @code{reset-init} handler. + +A closely related issue is bus width. Jumpers might need to +distinguish between 8 bit or 16 bit bus access for the flash +used to start booting. + +@item @b{Peripheral Access} ... +Development boards generally provide access to every peripheral +on the chip, sometimes in multiple modes (such as by providing +multiple audio codec chips). +This interacts with software +configuration of pin multiplexing, where for example a +given pin may be routed either to the MMC/SD controller +or the GPIO controller. It also often interacts with +configuration jumpers. One jumper may be used to route +signals to an MMC/SD card slot or an expansion bus (which +might in turn affect booting); others might control which +audio or video codecs are used. + +@end itemize + +Plus you should of course have @code{reset-init} event handlers +which set up the hardware to match that jumper configuration. +That includes in particular any oscillator or PLL used to clock +the CPU, and any memory controllers needed to access external +memory and peripherals. Without such handlers, you won't be +able to access those resources without working target firmware +which can do that setup ... this can be awkward when you're +trying to debug that target firmware. Even if there's a ROM +bootloader which handles a few issues, it rarely provides full +access to all board-specific capabilities. + + @node Config File Guidelines @chapter Config File Guidelines |