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Interface Operation
The HP 16500C Logic Analysis System can be programmed by a controller
over RS-232-C 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 controlling
an HP 16500C Logic Analysis System over RS-232-C, 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 interface, XON/XOFF must be
used to handle protocol between the devices. For an extended hardwire
interface, protocol may be handled either with XON/XOFF or by
manipulating the CTS and RTS lines of the RS-232-C link. In all cases, the
DCD and DSR lines to the Logic Analysis System must remain high for proper
operation.
With extended hardwire operation, a high on the CTS line allows the Logic
Analysis System to send data, and a low prevents the Logic Analysis System
from transmitting data. 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 a three-wire interface has no control over the CTS
line, internal pull-up resistors in the Logic Analysis System assure that this
line remains high for proper three-wire operation.
RS-232-C Cables
The correct cable for the RS-232-C interface depends on your specific
application and whether you use software or hardware handshake protocol.
The following paragraphs describe which lines of the HP 16500C Logic
Analysis System are used to control the handshake operation of RS-232-C
relative to the system. To locate the proper cable for your application, refer
to the reference manual for your computer or controller. It should describe
the exact handshake protocol your controller can use to operate over an
RS-232-C bus. In this chapter you will also find HP cable recommendations
for hardware handshake.
Programming Over RS-232-C
Interface Operation
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