Chapter 2
Hardware Overview
GPIB-120B User Manual
2-2
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System Controller Detection (SC)
After you power on, Bus A and Bus B System Controller states are false.
If a GPIB device on Bus A asserts IFC or REN, the Bus A System
Controller state becomes true, and the Bus B System Controller state
becomes false.
If a GPIB device on Bus B asserts IFC or REN, the Bus B System
Controller state becomes true and the Bus A System Controller state
becomes false.
Active Controller Detection (AC)
After you power on, Bus A and Bus B Active Controller states are false.
If a GPIB device on Bus A asserts ATN, the Bus A Active Controller state
becomes true and the Bus B Active Controller state becomes false.
If a GPIB device on Bus B asserts ATN, the Bus B Active Controller state
becomes true and the Bus A Active Controller state becomes false.
Source Handshake Detection (SH)
A device is considered a source handshaker if it is an active Controller
sourcing command bytes or if it is a Talker sourcing data bytes.
After you power on, Bus A and Bus B Source Handshake states are false.
If a GPIB device on Bus A asserts DAV, the Bus A Source Handshake state
becomes true and the Bus B Source Handshake state becomes false.
If a GPIB device on Bus B asserts DAV, the Bus B Source Handshake state
becomes true and the Bus A Source Handshake state becomes false.
Data Transfer Modes
The GPIB-120B isolator/expander has two data transfer
modes—unbuffered mode and buffered mode. The data transfer mode
determines how data is transmitted across the expansion. The switch
on the back of the GPIB-120B sets the operation mode of the GPIB
isolator/expander. The default switch setting is for unbuffered transfer
mode.
