Measurement Computing Isolator488 - Manual (Page 28)

Section 3 IEEE 488 Primer
3-7
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
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)