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Talk/Listen
Addresses
D-6 HP-IB Overview
Each HP-IB device has at least one talk and one listen
address unless the device is either totally transparent or
is a talk-only or listen-only device. Device addresses
are used by the active controller in the command mode
(ATN true) to specify the talker (via a talk address) and
the listener(s) ( via listen addresses). Only one device
may be addressed to talk at any one time.
The address of a device is usually preset at the
factory but may be set to another value during system
configuration. In the binary representation of the
address, the device address is the decimal equivalent of
the five least-significant bits of the address. (On HP-IB
devices with selector switches, these are the five address
switches). The address can be from 0 to 30 inclusive.
The sixth and sevength bits determine if the address
is a talk or listen address, respectively. High-level
HP-IB controllers typically configure these two bits
automatically. Table D-l lists the HP-IB adddresses if a
controller requires the talk and listen addresses.
The talk and listen addresses fall within the printable
ASCII character set. When
characters while ATN is true, it becomes addressed. The
ASCII character "?" (ASCII 31) unaddresses all devices
while ATN is true. The device address is used by HP-IB
controllers, most of which automatically send the talk
and listen address characters.
a
device receives one of these
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