National Instruments Corporation GPIB-1014P User Manual page 133

Appendix C
68000 Code
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CSEND: clrw count.L
CSEND1: btst #CO,ISR2.L
beq CSEND1
cmpw #count,d0
beq CSEND3
addw #1,count.L
movb (a0)+,CDOR.L
btst #ERR,ISR1
bne CSEND2
add1 #1,a0
bra CSEND1
CSEND2: movw #-1,d0
CSEND3: rts
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|
| * * * * * * * * * * * * * * * * * * * * * * * * *
| * COMMAND SEND - CSEND *
| * * * * * * * * * * * * * * * * * * * * * * * * *
|
| Summary:
| - Called by CMD to send interface command messages
|
| Assumptions on entry:
| - The GPIB-1014P is Active Controller
| - The d0 register contains the number of bytes to
| send
| - The a0 register contains the address oc cmdbuf
|
| Actions:
| - Initialize a count variable
| - Wait until the CDOR is empty
| - Write a byte and increment the counter
| - Check for a GPIB error
| - Loop until all bytes are transferred
| - On an error, set d0 to -1
|
| Status on return:
| - d0 register contains number of bytes sent or -1 if an
| error occurred
|
|
| Comments
|
| Initialize count variable
|
| Wait till CDOR is empty
|
| Have all commands been sent?
| Yes
| No--Increment counter and write
| the next command
| If there are no Listeners, return -1
| in d0 register
|
|
|
|
C-17
Sample Programs
GPIB-1014P User Manual