Control Lines - HP 8753E Programming And Command Reference Manual

rate of the slowest device connected to the interface. With most
computing controllers and instruments, the handshake is performed
automatically, making it transparent to the programmer.
The data bus also has five control lines. The controller uses these lines
to address devices and to send bus commands.
ATN (Attention)
SRQ (Service Request)
REN (Remote Enable)
HP-IB Programum 'ng and Command Reference Guide
This line is used exclusively by the
system controller. When this line
is true (low), all devices (whether
addressed or not) unaddress and
revert to an idle state.
The active controller uses this line
to define 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.
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.
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
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