Measurement Computing Digital HS - Manual (Page 46)

All
Ready
All
Ready
None
Ready
None
Ready
Valid Not
Valid
Not
Valid
Valid
1st Data Byte 2nd Data Byte
All
Accept
All
Accept
None
Accept
None
Accept
DIO1-8
(composite)
DAV
NRFD
NDAC
Source
Acceptor
Acceptor
IEEE Bus Handshaking
4.6 DATA LINES
The GPIB provides eight data lines for a bit parallel/byte serial data transfer. These
eight data lines use the convention of DIO1 through DIO8 instead of the binary
designation of D0 to D7. The data lines are bidirectional and are active low.
4.7 MULTILINE COMMANDS
Multiline (bus) commands are sent by the Active Controller over the data bus with
ATN asserted. These commands include addressing commands for talk, listen, Untalk
and Unlisten.
4.7.1 Go To Local (GTL)
This command allows the selected devices to be manually controlled. ($01)
4.7.2 Listen Address Group (LAG)
There are 31 (0 to 30) listen addresses associated with this group. The 3 most
significant bits of the data bus are set to 001 while the 5 least significant bits are the
address of the device being told to listen.
4.7.3 Unlisten (UNL)