HP 8753D, User Manual, Page: 625 / 678

A TN (Attention) The active controller uses this line to dene whether
the information on the data bus is command-oriented or
data-oriented. When this line is true (low), the bus is in the
command mode , and the data lines carry bus commands . When
this line is false (high), the bus is in the data mode , and the
data lines carry device-dependent instructions or data.
SRQ (Service Request) This line is set true (low) when a device requests service
and the active controller services the requesting device . The
network analyzer can be enabled to pull the SRQ line for a
variety of reasons such as requesting control of the interface ,
for the purposes of printing, plotting, or accessing a disk.
REN (Remote Enable) This line is used exclusively by the system controller . When this
line is set true (low), the bus is in the remote mode , and devices
are addressed by the controller to either listen or talk. When
the bus is in remote mode and a device is addressed, it receives
instructions from the system controller via HP-IB rather than
from its front panel (pressing 4 LOCAL 5 returns the device to
front-panel operation). When this line is set false (high), the
bus and all of the connected devices return to local operation.
EOI (End or Identify) This line is used by a talker to indicate the last data byte in a
multiple-byte transmission, or by an active controller to initiate
a parallel-poll sequence . The analyzer recognizes the EOI line
as a terminator , and it pulls the EOI line with the last byte of a
message output (data, markers , plots , prints , error messages).
The analyzer does not respond to parallel poll.
HP-IB Requirements
Number of Interconnected Devices: 15 maximum.
Interconnection P ath Maximum Cable Length: 20 meters maximum or 2 meters per device
(whichever is less).
Message Transfer Scheme: Byte serial, bit parallel a synchronous data
transfer using a 3-line handshake system.
Data Rate: Maximum of 1 megabyte-per-second over the
specied distances with tri-state drivers . A ctual
data rate depends on the transfer rate of the
slowest device connected to the bus .
A ddress Capability: Primary addresses: 31 talk, 31 listen. A
maximum of 1 talker and 14 listeners can be
connected to the interface at given time .
Multiple-Controller Capability: In systems with more than one controller (like
this instrument), only one controller can be
active at any given time . The active controller
can pass control to another controller , but only
the system controller can assume unconditional
control. Only one system controller is allowed.
Compatible P eripherals 11-17