HP 3325B - Page 48

Remote Operation via HP-IB
HP-IB Management (Control) Lines
AIN - Attention. This line is used by the active controller to define how information on the
data lines should be interpreted by other devices on the bus.
^en ATN is low (true) the HP-IB is in the command mode and the data lines should be
interpreted as bus commands (see “Bus Commands” later in this chapter). In the command
mode tM controller is active and ail other devices are waiting for instructions. Also, devices
on the HP-IB are addressed or unaddressed as listeners or talkers while the bus is in
command mode.
^en ATN is false the HP-IB is in data mode and the data lines should be interpreted as
device-dependent commands. In the data mode, data and instructions are transferred
between devices on the HP-IB. Instructions transferred to the instrument are called
All the commands specifically for the HP 3325B fall into this
categoiy. The HP 3325B device-dependent commands configure the HP 3325B, initiate
me^u^ments, initiate data transfers, or define error-reporting conditions. These
device-dependent commands are meaningless for other instruments. The HP 3325B
device-dqjendent commands are listed later in this chapter under the heading “HP 3325B
Remote Operation Command Set.”
SRQ Service Request This line is set low (true) by any instrument requiring service. The
controller should be programmed to respond to most service requests by polling the devices
on the bus to determine which one initiated the request. The HP 3325B responds to a serial
poll by putting its status byte on the data lines.
REN - Remote Enable The system controller must set REN low and then address specific
device(s) to listen before they can operate under remote control.
WO Interface Clear. Only the system controller can activate the IFC line. When IFC is
true (low), all devices on the bus become inactive
indicate the end of a multiple-byte transfer sequence
(m the data mode) or by the controller, m conjunction with ATN, to execute a parallel poll.
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