Measurement Computing Digital488 - Manual (Page 67)

Section 4 IEEE 488 Primer
4.7
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)