22
IEEE 488 BUS EXTENDER AND IEEE 488 FIBER BUS EXTENDER
5.5.2 N
OT
R
EADY FOR
D
ATA
(NRFD)
This line is used by the Listeners to inform the Talker when they are ready to
accept new data. The Talker must wait for each Listener to unassert this line
(high), which they will do at their own rate when they are ready for more data.
This assures that all devices that are to accept the information are ready to receive
it.
5.5.3 N
OT
D
ATA
A
CCEPTED
(NDAC)
The NDAC line is also controlled by the Listeners. This line indicates to the Talker
that each device addressed to listen has accepted the information. Each device
releases NDAC (high) at its own rate, but the NDAC will not go high until the
slowest Listener has accepted the data byte.
Figure 5-2. IEEE Bus Handshaking.
5.6 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.
5.7 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.
5.7.1 G
O
T
O
L
OCAL
(GTL)
This command allows the selected devices to be manually controlled. (IEEE 488
command code: $01.)
Содержание IC095A
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