Lpc2000

>> > intvect:
>> > 
>> >         LDR     pc, startaddr
>> >         LDR     pc, undefinstaddr
>> >         LDR     pc, softintaddr
>> >         LDR     pc, preabortaddr
>> >         LDR     pc, dataabortaddr
>> >         .word   0xb8a06f60
>> >         LDR     pc, interruptaddr
>> >         LDR     pc, fastintaddr
>> > 
>> > startaddr:
>> >         .word   start
>> > 
>> > undefinstaddr:
>> >         .word   undefined_instruction_routine
>> > 
>> > softintaddr:
>> >         .word   software_interrupt_routine
>> > 
>> > preabortaddr:
>> >         .word   prefetch_abort_routine
>> > 
>> > dataabortaddr:
>> >         .word   data_abort_routine
>> > 
>> > interruptaddr:
>> >         .word   interrupt_routine
>> > 
>> > fastintaddr:
>> >         .word   fast_interrupt_routine
>> > 

> The Hard Coded way...not bad at all.

I'm sure that you understand this, but for those that don't, let me
mention that the checksum is done over the first 8 integers (32 bit
integers) of flash memory excluding the area where the checksum is
stored. That is, in the assembly code above, the stuff between the
label "intvect:" and the label "startaddr".

Although the location for start and all of the routines may change as
code is developed, all of those changes happen after the label
"startaddr:" (as resolved by the linker).

The net result is that the first 32 bytes (address 0000 to 001F)
will always contain the same values, and thus the checksum (two's
compliment sum) will also remain the same. The hex file will have
these first two lines: 

:10 0000 00 18F09FE5 18F09FE5 18F09FE5 18F09FE5 C0
:10 0010 00 18F09FE5 606FA0B8 14F09FE5 14F09FE5 1D

(I added spaces to make it easier to understand.)

You can see the ".word   0xb8a06f60" in the hex file which is the
two's compliment sum of the other integers. (Note the byte order is
reversed.) 0xb8a06f60 doesn't need to change, even when the routines
move.

So no need for any external program to do the calculation each time
that the source is compiled.

I anticipate using a loader other than the Philips utility, so I
wanted to resolve the checksum calculation without needing to use the
Philips utility. This way the hex file has the checksum.


[Insomnia is no fun...]

-Rob

>> You can load your HEX file in the the flash utility, generate the 
>> checksum (Vector calc button in the flash screen) and save the HEX 
>> file back.
>> 
>> Richard

> That's pretty close to what I'm currently doing before updating the 
> firmware using IAP calls (not the ISP utility) during code execution.

> Both would work for me. Thanks.

> Leighton







 
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