Hi there, I am struggling with a problem on my lh75411 MCU (arm7) which concerns the endianness. I observed that the endianness changes sometimes when uploading a srec file after reset to the MCU. I am using the following script for the M*craigor OCD tool: conn endian little CPSR = 0x13 r13 = 0x2100 r14 = 0x2200 byte 0xfffe2008 = 0x01 word 0xfffe5000 = 0x00005B3F word 0xFFFF1004 = 0x00000400 word 0xFFFF1008 = 0x00000400 download dh75411_program_sram_example.srec dasm go Sometimes after uploading the (little-endian) programme into the internal SRAM, the programme is not processed properly: steping from 0x0 on shows that the branch commands are ignored and the PC simply steps to the next address. The MCU obviously does not "understand" the opcodes. By compiling in big endian code, the same programme works fine (till the MCU is switching back to little endianness). From the documentation for the lh754xx I learned that the static memory controller assumes little endianness, and from the arm7 doc, I learned that the processor can run in both modes. My question: 1. Is it possible that the endianness changes from reset to reset? 2. Is there a code snippet which allows defining the endianness for arm7? Thanks a lot in advance! Daniel
Defining the endianness for arm7 MCU
Started by ●April 23, 2004
Reply by ●April 23, 20042004-04-23
On 23 Apr 2004 01:51:08 -0700, Daniel <hansch@cms.tecmath.de> wrote:> My question: > 1. Is it possible that the endianness changes from reset to reset?I am not familiar with the part, but usually ARM-based processors have a pin that defines the endianness on reset. It might be floating.> 2. Is there a code snippet which allows defining the endianness for > arm7?No. It is done in hardware. Vadim
Reply by ●April 26, 20042004-04-26
Vadim, I've found in the arm7 docs that the endianness can be changed by using the co-processor register p15: MOV r14, #0x80 ; Set BIGEND MCR p15, 0, r14, c1, c0 I didn't try this yet, since my OCD debugger does not know the register p15 for setting it manually! Additionally, right after reset, the first command (at 0x00) being processed is a relative Branch to the reset handler. If the MCUs endianness does not fit to the endianness of the uploaded code, then the MCU simply ignores the branch command (i.e. the PC goes to the next address which is 0x04). This makes me crazy! Further ideas? Vadim Borshchev <vadim.borshchev@127.0.0.1> wrote in message news:<opr6w1twn6y1ubid@news>...> On 23 Apr 2004 01:51:08 -0700, Daniel <hansch@cms.tecmath.de> wrote: > > > My question: > > 1. Is it possible that the endianness changes from reset to reset? > > I am not familiar with the part, but usually ARM-based processors have a > pin that defines the endianness on reset. It might be floating. > > > > 2. Is there a code snippet which allows defining the endianness for > > arm7? > > No. It is done in hardware. > > Vadim
