Table of Contents
Advertisement
IEEE-488 PROGRAMMING
Figure 4-5. Contact
Assignments
4.4 INTERFACE
FUNCTION
CODES
The interface
function
codes, which
are part of the
lEEE-488 standards, define an instrument's
ability to sup-
port various interface functions,
and they should not be
confused with programming
commands found elsewhere
in this manual. Interface function codes for the Model 194
are listed in Table 4.3 and are listed for convenience on the
rear panel adjacent to the IEEE-488 connector. The codes
define Model 194 capabilities
as follows:
SH (Source Handshake)-SHl
defines the ability of the
Model 194 to properly handshake data or command bytes
when the unit is acting as a source.
AH (Acceptor Handshake)-AH1
defines the ability of the
Model 194 to properly
handshake the bus when it is ac-
ting as an acceptor of data or commands.
T (Talker)Jhe
ability of the Model 194 to send data over
the bus to other devices is defined by the T function. Model
194 talker capabilities
exist only after the instrument
has
L7T (Device Trigger)-The
ability for the Model 194 to have
its readings triggered is defined by the tYI function.
C (Controller)-The
Model 194 does not have controller
capabilities.
TE (Extended Talker)-The
Model 194 does not have ex-
tended talker capabilities.
LE (Extended Listener)-The
Model 194 does not have ex-
tended listener capabilities.
E (Bus Driver Type)-The
Model 194 has open-collector bus
drivers.
Table 4-3. Model 194 Interface
Function
Codes
Code
Interface
Function
SHl
Source Handshake
Capability
AH1
Acceptor Handshake
Capability
T6
Talker (Basic Talker, Serial Poll, Unaddressed
To Talk On MLA)
L4
Listener (Basic Listener, Unaddressed
To
Listen On MTA)
SRl
Service Request Capability
RLI
Remote/Local
Capability
PPO
No Parallel Poll Capability
DC1
Device Clear Capability
Dll
Device Trigger Capability
co
No Controller
Capability
El
Open Collector Bus Drivers
TEO
No Extended Talker Capabilities
LEO
No Extended
Listener Capabilities
been addressed to talk.
4.5 PRIMARY
ADDRESS
SELECTION
L (Listener)-The
L function
defines the ability
of the
Model 194 to receive device-dependent
data over the bus.
Listener capabilities
exist only after the instrument
has
been addressed to listen.
SR (Service Request)-The
SR function
defines the ability
of the Model 194 to request service from the controller.
RL (Remote-Local)-The
RL function
defines the capabili-
ty of the Model 194 to be placed in the remote or local
modes.
PP (Parallel Poll)-The
Model 194 does not have parallel
polling
capabilities.
DC (Device Cl&x)-The
DC function defines the ability of
the Model 194 to be cleared (initialized).
The Model 194 must receive a listen command before it
will
respond
to addressed
commands
over the bus.
Similarly,
the instrument
must receive a talk command
before it will transmit its data. These listen and talk corn-
mands are derived from the primary address of the instru-
ment, which is set to 9 at the factory. Until you become
more familiar with your instrument,
it is recommended
that you leave the address at this value because the pro-
gramming examples in this manual assume the instrument
is programmed
for that address.
The primaly
address can be programmed
for any value
between 0 and 30. However, each device on the bus must
have a unique primary
address-- a factor that should be
kept in mind when setting the primary
address of the
4-6
Advertisement
Table of Contents
