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#asm branch instruction not supported?

 
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#asm branch instruction not supported?
PostPosted: Thu May 27, 2004 3:58 am     Reply with quote
Code:

    #ASM
      rrcf   TMR1H, 0    // rotate timer 1 register through carry
      bc      3           // if carry then jump 3 further
      movlw   0           // clear w register
      movwf   LATB        // set port B
      bra      3           // jump 3 further
      movlw   16          // set bit 5 of w register
      movwf   LATB        // set port B
      nop               // nop
      nop               // nop
    #ENDASM


When I compile, I get an error 'Expecting an identifier'. When I comment out the 'bc' and the 'bra' instruction, it works.

Is the branch not correct?

Using v3.179
Ttelmah
Guest
Re: #asm branch instruction not supported?
PostPosted: Thu May 27, 2004 4:48 am     Reply with quote
Anonymous wrote:
Code:

    #ASM
      rrcf   TMR1H, 0    // rotate timer 1 register through carry
      bc      3           // if carry then jump 3 further
      movlw   0           // clear w register
      movwf   LATB        // set port B
      bra      3           // jump 3 further
      movlw   16          // set bit 5 of w register
      movwf   LATB        // set port B
      nop               // nop
      nop               // nop
    #ENDASM


When I compile, I get an error 'Expecting an identifier'. When I comment out the 'bc' and the 'bra' instruction, it works.

Is the branch not correct?

Using v3.179


Use a label.
So:
[code]
#ASM
rrcf TMR1H, 0 // rotate timer 1 register through carry
bc 3 // if carry then jump 3 further
movlw 0 // clear w register
movwf LATB // set port B
bra past // jump past
movlw 16 // set bit 5 of w register
movwf LATB // set port B
past:
nop // nop
nop // nop
#ENDASM
[code]

Best Wishes
Guest
PostPosted: Thu May 27, 2004 5:32 am     Reply with quote
Honestly I can't find that in the 18FXX2 datasheet...

Code:
HERE BC 5

Should execute as follows:
Quote:
Before instruction:
PC = address (HERE)
After instruction:
If Carry: PC = address (HERE + 12)
If no Carry: PC = address (HERE + 2)

Which should mean the BC instruction needs a relative address and not a label. Still PCWH comes up with an error... Question
Ttelmah
Guest
PostPosted: Thu May 27, 2004 7:07 am     Reply with quote
Anonymous wrote:
Honestly I can't find that in the 18FXX2 datasheet...

Code:
HERE BC 5

Should execute as follows:
Quote:
Before instruction:
PC = address (HERE)
After instruction:
If Carry: PC = address (HERE + 12)
If no Carry: PC = address (HERE + 2)

Which should mean the BC instruction needs a relative address and not a label. Still PCWH comes up with an error... Question


Understand, that the compiler does _not_ accept standard Microchip assembler. The syntax is closer to a C/ASM hybrid. It expects to receive a 'target', and work out for itself the offset value that is needed, rather than receiving the offset directly. You have to comply with the CCS form, rather than the Microchip form. Unfortunately, CCS, document this really badly....
The BC instruction, and the BRA instruction using a label compiles fine for me.

Best Wishes
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