Tektronix 372, User Manual, Page: 283 / 364

GPIB
372 User Manual
3Ć171
H Controller - Can manage the bus, send commands, receive data and
status, and control the flow of the data. The system controller acts as a
talker and as a listener. The GPIB system must be controlled by only one
controller at a time. However, controllers can pass control to another
controller on the bus, and assume a talker/listener role.
Restrictions
GPIBĆconfigured devices are distributed on the bus according to these
rules:
1. No more than 15 devices total (including the controller) can be included
on a signal bus.
2. To maintain electrical characteristics of the bus, one device must be
connected for every 2 m of cable (generally each device represents one
device load to the bus).
3. The total cable length (cumulative) must not exceed 20 m.
4. At least twoĆthirds of the device loads must be powered on.
The voltages and current values required at connector nodes are defined. All
specifications are based on the use of TTL (Transistor/Transistor Logic)
technology. Message can be sent as either active or passive true signals.
Functional Elements
Interface functions provide the facilities through which devices send, proĆ
cess, and receive messages by IEEE Std 488.1-1987. The abbreviations for
these functions, which are in parentheses, are taken from the IEEE Std
488.1-1987 and are commonly used when describing the functions.
Table 3Ć51 shows which GPIB interface functions are implemented in the
372.
TableĂ3Ć51:ăGPIB Interface Functions/Implemented Subset
Interface Function IEEE STD 488.2
PORT
Capability
Acceptor Handshake
(AH)
AH1 Complete capability
Source Handshake
(SH)
SH1 Complete capability
Listener (L) L4 Basic Listener, unaddress if
MTA, no Listen Only Mode
Talker (T) T5 Complete capability
Device Clear (DC) DC1 Complete capability
Remote/Local (RL) RL1 Complete capability
Service Request (SR) SR1 Complete capability