Interface Operation; Rs-232C Cables - Agilent Technologies HP 16500B Manual

Programming Over RS-232C

Interface Operation

Interface Operation
The HP 16500B Logic Analysis System 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 16500B Logic Analysis System over RS-232C with a
controller, you are normally operating 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 a 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 logic
analysis system must remain high for proper operation.
With extended hardwire operation, a high on the CTS input allows the logic
analysis system to send data, and a low disables the logic analysis system
data transmission. Likewise, a high on the RTS line allows the controller to
send data, and a low signals a request for the controller to disable data
transmission. Because three-wire operation has no control over the CTS
input, internal pull-up resistors in the logic analysis system assure that this
line remains high for proper three-wire operation.

RS-232C Cables

Selecting a cable for the RS-232C interface depends on your specific
application, and, whether you wish to use software or hardware handshake
protocol. The following paragraphs describe which lines of the HP 16500B
Logic Analysis system are used to control the handshake operation of the
RS-232C relative to the system. To locate the proper cable for your
application, refer to the reference manual for your computer or controller.
Your computer or controller manual should describe the exact handshake
protocol your controller can use to operate over the RS-232C bus. Also in
this chapter you will find HP cable recommendations for hardware handshake.
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