HP Sander 16500C manual Interface Operation, RS-232-C Cables

Programming Over RS-232-C

Interface Operation

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.

3–3