General GPIB Information 1-5 IEEE-488 Interface Bus Description
MG369xC GPIB PM PN: 10370-10374 Rev. F 1-7
Message Types
There are three types of information transmitted over the GPIB—interface function messages, device-specific
commands, and data and instrument status messages.
Interface Function Messages
The controller manages the flow of information on the GPIB using interface function messages, usually
called commands or command messages. Interface function messages perform such functions as
initializing the bus, addressing and unaddressing devices, and setting device modes for remote or local
operation.
There are two types of commands—multiline and uniline. Multiline commands are bytes sent by the
active controller over the data bus (DIO1–DIO8) with ATN set TRUE. Uniline commands are signals
carried by the individual interface management lines.
The user generally has control over these commands; however, the extent of user control depends on the
implementation and varies with the specific GPIB interface hardware and software used with the
external controller.
Device-Specific Commands
These commands are keywords or mnemonic codes sent by the external controller to control the setup
and operation of the addressed device or instrument. The commands are normally unique to a particular
instrument or class of instruments and are described in its documentation.
Device-specific commands are transmitted over the data bus of the GPIB to the device in the form of
ASCII strings containing one or more keywords or codes. They are decoded by the device’s internal
controller and cause the various instrument functions to be performed.
Table 1-2. MG369xC Interface Function Capability
Function Identifier Function MG369xC Capability
AH1 Acceptor Handshake Complete Capability
SH1 Source Handshake Complete Capability
T6 Talker No Talk Only (TON)
L4 Listener No Listen Only (LON)
SR1 Service Request Complete Capability
RL1 Remote/Local Complete Capability
PP1 Parallel Poll Complete Capability
DC1 Device Clear Complete Capability
DT1 Device Trigger Complete Capability
C0, C1, C2, C3, C28 Controller Capability Options C0, No Capability
C1, System Controller
C2, Send IFC and Take Charge
C3, Send REN
C28, Send IF Messages
E2 Tri-State Drivers Three-state bus drivers
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