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Programming Over RS-232C
Introduction
Interface
Operation
HP 1650B/HP 16518
This section describes the interface functions and some general concepts
of the RS-232C. The RS-232C interface on this instrument is
Hewlett-Packard's implementation of EL4 Recommended Standard
Communications Equipment Employing Serial Binary Data Interchange."
With this interface, data is sent one bit at a time and characters are not
synchronized with preceding or subsequent data characters. Each
character is sent as a complete entity without relationship to other events.
The HP 1650B/51B can be programmed with a controller over RS-232C
using either a minimum three-wire or extended hardwire interface. The
operation and exact connections for these interfaces are described in
more detail in the following sections. When you are programming an HP
directly between two DTE (Data Terminal Equipment) devices as
compared to operating between a DTE device and a DCE (Data
Communications Equipment) device. When operating directly between
two DTE devices, certain considerations must be taken into account. For
three-wire operation, XON/XOFF must be used to handle protocol
between the devices. For extended hardwire operation, protocol may be
handled either with XON/XOFF or by manipulating the CTS and RTS
lines of the RS-232C link. For both three-wire and extended hardwire
operation, the DCD and DSR inputs to the HP 1650B/51B must remain
high for proper operation. With extended hardwire operation, a high 0;
the CTS input allows the HP 1650B/51B to send data and a low on this
line disables the HP 1650B/51B data transmission. Likewise, a high on the
RTS line allows the controller to send data and a low on this line signals a
request for the controller to disable data transmission. Since three-wire
operation has no control over the CTS input, internal pull-up resistors in
the HP 1650B/51B assure that this line remains high for proper three-wire
operation.
Programming Over RS-232C
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