Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 322)

III. COMMAND REFERENCES - 15. Command References 15A. Driver488/DRV Commands
Personal488 User’s Manual, Rev. 3.0 III-307
The CMD subcommand sends the data bytes with Attention ( ATN ) asserted. This ATN tells the bus
devices that the characters are to be interpreted as IEEE 488 bus commands, rather than as data. EOI is
not asserted during CMD transfers. For example, CMD &H3F is the same as UnListen ( UNL ). Note that it
is not possible to assert EOI during the transfer of a command byte, because EOI and ATN together
specify Parallel Poll ( PPOLL ).
The maximum length of the SEND command, including any subcommands, is 255 characters. If large
amounts of data must be transferred using the SEND command, then multiple SEND commands must be
used so that they are each less than 255 characters long. For example:
PRINT#1,”SEND UNT UNL MTA LISTEN 16 DATA 1,2,3,4,5,6”
is equivalent to:
PRINT#1,”SEND UNT UNL MTA LISTEN 16”
PRINT#1,”SEND DATA 1,2,3”
PRINT#1,”SEND DATA 4,5,6”
In this way, a long SEND command can be broken up into shorter commands.
SPOLL
SYNTAX SPOLL [addr]
addr is a device address (primary with optional secondary) or an external device
name.
RESPONSE 0 or 64 (without addr)
Number in the range 0 to 255 (with addr)
MODE CA
BUS STATES ATN
•UNL, MLA, TAG, SPE, *ATN, ATN•SPD, UNT
SEE ALSO SPOLL LIST, PPOLL
EXAMPLES PRINT#1,”SPOLL 16” Serial Poll device 16
INPUT#2,SPSTAT Receive the SPOLL status
IF SPSTAT AND 64 THEN Test rsv...
PRINT#1,”SPOLL” Check the SRQ status
INPUT#2,SRQ Receive the SRQ status
IF SRQ<>0 THEN If SRQ is asserted then ...
In Active Controller mode, the SPOLL (Serial Poll) command performs a Serial Poll of the bus device
specified and responds with a number from 0 to 255 representing the decimal equivalent of the eight-
bit device response. If rsv ( DIO7 , decimal value 64 ) is set, then that device is signaling that it requires
service. The meanings of the other bits are device-specific.
Serial Polls are normally performed in response to assertion of the Service Request ( SRQ ) bus signal by
some bus device. In Active Controller mode, with no bus address specified, the SPOLL command
returns the internal SRQ status. If the internal SRQ status is set, it usually indicates that the SRQ line is
asserted. Driver488 then returns a 64 . If it is not set, indicating that SRQ is not asserted, then
Driver488 returns a 0 .
In Peripheral mode, the SPOLL command is issued without an address, and returns the Serial Poll
status. If rsv ( DIO7 , decimal value 64 ) is set, then Driver488 has not been Serial Polled since the
issuing last REQUEST command. The rsv is reset whenever Driver488 is Serial Polled by the
Controller.