On Fri, Jul 8, 2011 at 6:30 PM, Mahr, Stefan <stefan.m...@sphairon.com> wrote: >>>> How do they convert then, when they do not know from which endianes to >>>> convert from ? >>> >>> Conversion is done from byte array of jtag chain. >> How ? > > buf_get_u32 does conversion from uint8* array > > example: > mips_ejtag_get_impcode (mips_ejtag.c) > > field.in_value is filled by jtag_add_dr_scan with 4 times uint8. > buf_get_u32 converts byte array to host endian uint32
How ? It does not convert anything. It just takes the data and puts it into array, in the order that it comes. >>> The endianness of MIPS EJTAG tap seems to have always the same endianness, >>> no matter of MIPS CPU memory endianness. >> What makes you think so ? > > Because openocd works in all combinations of BE and LE host and target. (If > you > revert commit 2482244b0788c007dd789c21a4416379c229ea5c.) So yes, it's just a > guess. Which might mean that all commands are sent to EJTAG in appropriate target format in which CPU expects them (be it BE or LE, depends in which mode it runs). > Could this be the explanation: > > http://downloads.buffalo.nas-central.org/LS2_MIPSel/DevelopmentTools/JTAG/MD00047-2B-EJTAG-SPC-03.10.pdf > Page 97: > Byte 0 refers to bits 7:0, byte 1 refers to bits 15:8, byte 2 refers to bits > 23:16, and byte 3 refers to bits > 31:24, independent of endianess. > This is _always_ the case in _all_ architectures. But, as you see, this Byte0 is put to lower addresses for LE and to higher for BE. This is always the case. > Please also see Chapter 6.3.3, 6.3.6, 6.4.1, etc. TAPs are alway LSB first, > so endianness doesn't matter here. This is always the case, for all JTAG TAPS. No, there must be something else... BR, Drasko _______________________________________________ Openocd-development mailing list Openocd-development@lists.berlios.de https://lists.berlios.de/mailman/listinfo/openocd-development
