[sdiy] DSPIC branches GOTOs etc,

[Richie Burnett]

Thinking about this some more, since GOTO instructions take up two 
consecutive program memory locations, then this code snippet shouldn't 
work...

dma_wait:
BTSS    IFS0,#DMA1IF    ; Check DMA1 transfer complete flag and skip next 
instruction if it is set
GOTO    dma_wait        ; Loop back and wait until DMA transfer is complete 
if flag is still clear
<code here to deal with DMA data>

The BTSS or BTSC followed by GOTO appears throughout my code and works fine, 
even though the bit-test instruction only skips *one* program memory 
location if the tested condition is true.  The only reason it must work is 
because the second word of the GOTO instruction (the address) is executed as 
a NOP.  I guess I should go through my program changing all the GOTOs that 
follow BTSS or BTSC with BRA instructions instead, just in case Microchip 
alter this behaviour in future!?

It's also interesting to note that a CALL instruction to an address label is 
also coded as two words of program memory.  So using BTSS or BTSC to 
conditionally jump over a subroutine CALL would also appear to be on shaky 
ground!

-Richie,