User`s guide

4-3
Programming over RS-232-C
Interface Operation
Interface Operation
The oscilloscope 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
subsequent sections of this chapter. When you are programming the
oscilloscope 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, certain considerations
must be taken 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 oscilloscope. For
both three-wire and extended hardwire operation, the DCD and DSR inputs to
the oscilloscope must remain high for proper operation.
With extended hardwire operation, a high on the CTS input allows the
oscilloscope to send data and a low on this line disables the oscilloscope 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 oscilloscope ensure that this line remains high
for proper three-wire operation.
Cables
Selecting a cable for the RS-232-C interface is dependent on your specific
application. The following paragraphs describe which lines of the oscilloscope
are used to control the operation of the RS-232-C bus relative to the
oscilloscope. 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.