Relation Of Atn And The Handshake Lines (Rfd. Dac. Dav) - HP 5340A Operating And Service Manual

When the controller sets ATN low, all 5340As will set DAC to its valid state within 200
nsec. When the controller sets ATN high, the 5340A's that have not been addressed to
listen will not drive DAC, those addressed to listen will set DAC to its valid state within
200 nsec.
The listener must not set DAC low until it senses DAV is high. It may do so before or at
the same time that it sets RFD high. It must not return DAC high until it senses DAV is
low and may do s o after or at the same time that it sets RFD low.
h. DATA VALID (DAV)
DAV is the handshake line that indicates the validity of information on the data lines. Its
relationship to the other handshake lines and ATN is shown in Figure 2-1 and Table 2-1.
It is driven by TALKERS: the controller when ATN is low and by the instrument
talk when ATN is high. It is sensed by LISTENERS: all, 5340A's if ATN
addressed
to
is low and by the instruments addressed to listen when ATN is high.
When DAV is low, the states of data lines DIOl through D107 are unconditionally valid
and may be accepted by all listeners at their own time. To allow for cable rise time,
ringing, etc., the 5340A, when addressed to TALK, does not set DAV low until 2 ysec
after it has placed valid data
taken similar precautions. DAV can only be driven low if RFD and
DAV is high, the information on the data lines is not valid. DAV cannot be set high
unless DAC is high and RFD is low.
Table 2-1. Relation of ATN and the Handshake Lines (RFD, DAC, DAV)
READY FOR DATA
STATE OF
ATTENTION
LINE (ATN)
LOW
One or more
not
ready for
data
L
0
ADDRESS
MODE W
(1) Driven by
(2) Sensed by controller
drives
(3) 5340A's
data
for
DATA I
MODE G
H
Driven
(1) by
(2) Sensed by
(3) All instrqments not addressed
at its output connector. It assumes that the controller has
HIGH LOW
One or
All
ready
are
not accepted
for data
the data
all 5340As
valid state
to its within 200 ns of
accepted
LISTEN
to
addressed
instrument to TALK
w ill not drive
Installation and Remote Programming
IFC
DATA ACCEPTED
HIGH
Controller
more All
has valid
have
data on
accepted
the data lines
(1) Driven by controller
(2) Sensed
ATN
going low
The
TALKER has
accepted valid data
have
the
data on
data
(1) Driven
(2)
Model 5340A
are high. When
LOW HIGH
Controller's
data not
valid
by
The
addressed
addressed
TALKERS
not
data
lines
valid
the instruments
by
addressed to TALK
Sensed ALL instruments
by
to LISTEN
addressed
2-5