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Section IV
Model
DRC-93C
REN (Remote Enable), EOI (End or
cepted)
.
Signals on these lines operate
Identify) and the SRQ
(Service
in
an
interlocking hand-shake
request) manage the bus and control
mode.
The two signal lines, NRFD
the orderly flow of commands on the
and NDAC, are each connected in a
bus.
The IFC, ATN, and REN manage-
logical AND to all devices
connected
to
ment lines are issued only by the
the bus.
BUS
CONTROLLER.
The DAV line is pulled low by the TALKER
The IFC (Interface Clear) management
after it places its data on the
line is pulled low by the
BUS
DATA lines. This tells the LISTENERS
CONTROLLER
to clear the interface.
that information on the DATA lines
is valid.
A LISTENER holds the
The ATN (Attention) line is the
NRFD line low to indicate it is not
management line used by the
BUS
ready. Since these lines are connected
CONTROLLER
to get the attention of
in a logical AND to all other
the devices on the bus. The
B U S
devices, then the NRFD line will
CONTROLLER
does this by pulling the
not go high until all of the devices
ATN
line low and sending talk or
are ready.
listen addresses on the DATA lines.
When the ATN line i s low, all
The NDAC line is pulled low by a
devices listen to the DATA lines.
LISTENER while it is receiving the
When the ATN line goes high, then
DATA and lets it go high when the
the devices addressed to send or
DATA is captured.
Since the NDAC
receive data (for example, the DRC-
lines of all devices are connected
93C) perform their functions while
in a logical AND, the NDAC line
all others ignore the DATA lines.
will not go high until all devices
The REN (Remote Enable) management
line is pulled low by the
BUS
4.3
INTERFACE CAPABILITIES
CONTROLLER
to enable a device (the
DRC-93C) to perform the functions
The IEEE-488 Interface capabilities
of TALKER or LISTENER.
of the Model DRC-93C are listed
in Table
4-1
as well as in mnemonic
The EOI (End or Identify) management
format on the instrument's rear
line is pulled low by the
BUS
panel.
CONTROLLER
or a TALKER (the DRC-93C)
to indicate the end of a multiple
T a b l e 4 - 1 .
Interface Functions.
byte transfer sequence. Also the
EOI line along with the ATN line
are pulled low by the BUS CONTROLLER
to execute a polling sequence.
The SRQ (Service Request) management
line is pulled low by a device (for
example, the DRC-93C) to signal the
BUS CONTROLLER that a process is
completed, a limit, overload or
error encountered.
In some cases
this means that service is required.
Transfer of the information on the
data lines is accomplished through
the use of the three signal lines:
DAV (Data Valid), NRFD (Not Ready
for Data) and NDAC (Not Data Ac-
have received the DATA.
4-2
Mnemonic Interface Function Name
SH1
AH1
T5
L4
SR1
RL1
PPO
DC1
D T O
co
El
Source Handshake Capability
Acceptor Handshake Capability
Basic TALKER, serial poll cap-
ability, Talk only, Unaddressed
to Talk if addressed to Listen
Basic LISTENER, Unaddressed to
Listen if addressed to Talk
Service Request capability
Complete Remote/Local capablty
No Parallel Poll capability
Full Device Clear capability
No Device Trigger capability
No System Controller capablty
Open Collector Electronics
COPYRIGHT
3/88
LSCI
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