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WJ-8718A/MFP
FIGURE 3-11
TE controls the direction of DAV, NDAC, and NRFD.
When TE is high, DAV=T,
NDAC=R, and NRFD=R. (T = transmit; R = receive.)
DC controls the direction of IFC, REN, SRQ, and ATN. Wh€:n DC is high, IFC = R,
REN = R, SRQ = T, and ATN = R.
ATN is a normal transceiver channel that functions additionally as an internal
direction control or talk enable for EOI, whenever the TE and DC inputs are in the same state.
3.3.1.6
GPIB (General Purpose Interface Bus), (U1)
The GPIB (IEEE-488) Interface, 01, is a peripheral device designed to interfaee the
microprocessor in the receiver control block with the IEEE-488 bus.
Functions of the GPIB
Interface include data transfer, handshake protocol, talk/listen addressing procedures, device
clearing and triggering, service requests, and both serial and parallel polling schemes. Refer to
Figure 3-11, the GPIB Interface Block Diagram to correlate the following functional
descriptions of
VI
components.
TO BUS
TRANSCEIV"ERS
INTERNAL
""vv
MICROPROCESSOR
W
DATA BUS
I
DATA BUS
I
..........
I
.A
DATA
':>
I
......
I
v
I
I
no
"""--
I
.....
8 READ
~
I
Kr--
REGISTERS
......
Kr-
""" BUS
I
CONTROL .....
>
>
...
I
......
....
AUXILIARY
I
(
:::::
;:
REGISTERS
....
.....
TR
I
CONTROL .....
>
.....
I
.....
..,
....::::::>
8 WRITE
~
I
REGISTERS
it
I
v
~
I
I
v
"
I
I
";..
MESSAGE
I
I
~
DECODER
I
14SS-A3UI
' "
Figure 3-11. GPIB Interface (Ul) Block Diagram
3-45
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