Measurement Computing Extender 488HS Rev.2.0 - Manual (Page 25)

Section 3 IEEE 488 Primer
3.7
3.6 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.
3.7 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.
3.7.1 Go To Local (GTL)
This command allows the selected devices to be manually controlled. ($01)
3.7.2 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.
3.7.3 Unlisten (UNL)
This command tells all bus devices to Unlisten. The same as
Unaddressed to Listen. ($3F)
3.7.4 Talk Address Group (TAG)
There are 31 (0 to 30) talk addresses associated with this group. The 3
most significant bits of the data bus are set to 010 while the 5 least significant
bits are the address of the device being told to talk.
3.7.5 Untalk (UNT)
This command tells bus devices to Untalk. The same as Unaddressed to
Talk. ($5F)