12f1822, serial RX under interrupt, echo program doesn't want to play

[Dick Ivers]

Hi Chris,
Could you post your corrected code? Myself and others also use 16F1 parts, so this is an important issue.

Thanks,
Dick

[Chris Barron]

Hello Dick

I tested the same code as above, changing the interrupt handler to the following

asm
myint:
    banksel PIR1
    btfss   PIR1,5
    goto    int_out
    bcf     PIR1,5
    banksel  RCREG
    movfw   RCREG
    banksel _RX_BYTE
    movwf   _RX_Byte
    banksel TXREG
    movwf   TXREG
    nop
    btfss   PIR1,TXIF
    goto    $-1
       
int_out:    
    retfie
endasm

If in doubt, add another banksel

I'm not using the code now but I did test it upon receipt of Darrel's input to check it out.
I have used this part as a battery cell monitor and I can recall scratching my head over the same issue as then.
Hopefully I'm twice bitten, third time shy

[Mike, K8LH]

Are you missing a bank select in that code snippet?

asm
myint:
    banksel PIR1            '                    |B0
    btfss   PIR1,RCIF       '                    |B0
    goto    int_out         '                    |B0
    bcf     PIR1,RCIF       '                    |B0
    banksel RCREG           '                    |B3
    movfw   RCREG           '                    |B3
    banksel _RX_BYTE        '                    |B?
    movwf   _RX_Byte        '                    |B?
    banksel TXREG           '                    |B3
    movwf   TXREG           '                    |B3
    nop                     '                    |B3
    btfss   PIR1,TXIF       '                    |B0 <-- *****
    goto    $-1             '                    |B0
       
int_out:    
    retfie
endasm

If _RX_Byte is in bank 0, then maybe this would work?

asm
myint:
    banksel PIR1            '                    |B0
    btfss   PIR1,RCIF       '                    |B0
    retfie                  '                    |B0
    bcf     PIR1,RCIF       '                    |B0
    banksel RCREG           '                    |B3
    movfw   RCREG           '                    |B3
    movwf   TXREG           '                    |B3
    banksel _RX_BYTE        '                    |B0
    movwf   _RX_Byte        '                    |B0
    btfss   PIR1,TXIF       '                    |B0
    goto    $-1             '                    |B0
    retfie                  '                    |B0
endasm

[Chris Barron]

Whatever.

Darrel's answer covered it.