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Programming over RS-232-C
Interface operation
Interface operation
The logic analyzer can be programmed with 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 programming the logic analyzer over
RS-232-C 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 RS-232-C devices, you must take
certain considerations into account. For three-wire operation, an XON/XOFF
software handshake must be used to handle handshaking between the
devices. For extended hardwire operation, handshaking may be handled
either with XON/XOFF or by manipulating the CTS and RTS lines of the logic
analyzer interface module. For both three-wire and extended hardwire
operation, the DCD and DSR inputs to the logic analyzer interface module
must remain high for proper operation.
With extended hardwire operation, a high on the CTS input allows the logic
analyzer to send data and a low on this line disables the logic analyzer 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. Because three-wire operation has no control over the CTS
input, internal pull-up resistors in the logic analyzer interface module ensure
that this line remains high for proper three-wire operation.
Cables
Selecting a cable for the RS-232-C interface depends on your specific
application. The following paragraphs describe which lines of the logic
analyzer are used to control the operation of the RS-232-C bus relative to the
logic analyzer. To locate the proper cable for your application, refer to the
reference manual for your controller. This manual should address the exact
method your controller uses to operate over the RS-232-C bus.
Minimum Three-wire Interface with XON/XOFF Software Handshake
With a three-wire interface, the software (as compared to interface
hardware) controls the data flow between the logic analyzer and the
controller. This provides a much simpler connection between devices
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