Interface Operation
The 1660-series logic analyzers 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 a
1660-series logic analyzer 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
analyzer 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 disables the logic analyzer 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 analyzer 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 1660-series
logic analyzer 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 cable recommendations for hardware handshake.
Programming Over RS-232C
Interface Operation
3–3