Thanks for the comments! On case sensitivity, I have the command line options set to /q and /c- , which should, I believe, turn off case sensitivity. Looking at the listing file, it looks like the macro gets converted to all upper case when substituted. Listing file below. Harold 0074 00301 ISR 00302 ; Determine cause of interrupt and do it. 00303 SAVECONTEXT ; Save registers M ; Save register context for isr. Swaps swap high and low halves of f with the result going either M ; back to f or to w. Swap is used here because they affect no status bits. 0074 00A0 M MOVWF ISRW ; Save W 0075 0E03 M SWAPF STATUS,W ; get status in W (including bank select bits) swapping hi/lo halves 0076 1283 M BCF STATUS,RP0 ; force to bank 0 0077 00A1 M MOVWF ISRSTATUS ; and save swapped status 0078 0804 M MOVF FSR,0 ; Get fsr in w 0079 00A2 M MOVWF ISRFSR ; and save it 00304 ; btfsc pir1,txif ; Check for tx ready 00305 ; call TxSerial ; Go send a byte 007A 1A8C 00306 BTFSC PIR1,RCIF ; check for received character 007B 2110 00307 CALL RXSERIAL ; Go get byte 007C 1B8C 00308 BTFSC PIR1,PSPIF ; Parallel slave port write? 007D 20C1 00309 CALL READPSP ; Go handle it 007E 190B 00310 BTFSC INTCON,T0IF ; Check for timer 0 interrupt 007F 214A 00311 CALL TIMER0ISR ; go handle it (which transmits a byte on dmx) 00312 RESTORECONTEXT 0080 0822 M MOVF ISRFSR,0 ; get old fsr 0081 0084 M MOVWF FSR ; and restore it 0082 0E21 M SWAPF ISRSTATUS,W ; get old status (including bsr bits) in w, swapping back to normal 0083 0083 M MOVWF STATUS ; restore it 0084 0EA0 M SWAPF ISRW,1 ; swap halves in isrw making them backwards 0085 0E20 M SWAPF ISRW,0 ; swap back to forward and in W without affecting status 0086 0009 00313 RETFIE On Thu, 17 Jul 1997 01:36:30 -0400 Mike Keitz writes: >Everything looks conventional and it should work. Check your .LST >file >to make sure it assembled properly. There is inconsistent use of >upper/lowercase in the labels in the code posted. The Microchip >assembler is case-sensitive. It may not tell you if it can't find >something in a macro. >-Mike >