Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 117)

8K. Other Languages II. SOFTWARE GUIDES - 8. Driver488/DRV
II-102 Personal488 User’s Manual, Rev. 3.0
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0 : A response of 0 indicates that Driver488/DRV is ready to receive a command. It has no data to
read, nor is it expecting data for output to the IEEE 488 bus. Driver488/DRV is forced into this
state by the
IOCTL BREAK command.
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1 : A response of 1 indicates that Driver488/DRV has a response ready to be read by the user’s
program. The program must read the response before sending a new command (except
IOCTL BREAK ) or a SEQUENCE - DATA HAS NOT BEEN READ error occurs.
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2 : A response of 2 indicates that Driver488/DRV is waiting for data to OUTPUT to the IEEE 488
bus. The user’s program must send the appropriate data with terminators as needed to
Driver488/DRV. Attempting to read from Driver488/DRV while it is waiting for data causes a
SEQUENCE - NO DATA AVAILABLE error.
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3 : A response of 3 indicates that Driver488/DRV is waiting for the completion of a command.
This is similar to a response of 2 except that Driver488/DRV is waiting for a command, rather than
for data to OUTPUT .
The IOCTL Read response can be read from Driver488/DRV as:
ioctlbufDB 0 ;IOCTL Read response buffer
ioctllenEQU $-ioctllen ;Length of buffer
mov AX,4402h ;IOCTL Read
mov BX,ieee ;File handle
mov CX,ioctllen ;# chars to read
mov DX,offset
ioctlbuf ;DS:DX - buffer
int 21h ;Execute DOS function
jc error ;Check for error
Data & Command Communication
Once Driver488/DRV has been opened, configured for RawMode communication, and reset with the
IOCTL Write command BREAK , we are ready to communicate with Driver488/DRV and control the
IEEE 488 bus. The BASIC commands:
PRINT#1,"HELLO"
LINE INPUT#1,A$
might be implemented in assembly language as:
cr EQU 0Dh ;Carriage-return
lf EQU 0Ah ;Line-feed
hello DB “HELLO”,,cr,,lf ;HELLO command with terminators
hellolen EQU $-hello ;HELLO command length
response DB 256 DUP (?) ;Place to put Driver488/DRV response
responselen EQ $-response ;Length of response buffer
recvdlen DW ? ;Place to keep # chars in response
mov AH, 40h ;DOS Write function
mov BX, ieee ;File handle
mov CX, hellolen ;Command length
mov DX, offset hello ;DS:DX - command
int 21h ;Execute DOS function
jc error ;Check for error
mov AH, 3Fh ;DOS Read function
mov BX, ieee ;File handle
mov CX, responselen ;Buffer length
mov DX, offset
response ;DS:DX - buffer
int 21h ;Execute DOS function
jc error ;Check for error
mov recvdlen, AX ;Save # of characters received
In this way, data and commands can be transferred to or from Driver488/DRV.