Minimum Three-Wire Interface with Software Protocol
With a three-wire interface, the software (as compared to interface
hardware) controls the data flow between the logic analyzer and the
controller. The three-wire interface provides no hardware means to control
data flow between the controller and the logic analyzer. Therefore,
XON/OFF protocol is the only means to control this data flow. The
three-wire interface provides a much simpler connection between devices
since you can ignore hardware handshake requirements.
The communications software you are using in your computer/controller must
be capable of using XON/XOFF exclusively in order to use three-wire interface
cables. For example, some communications software packages can use
XON/XOFF but are also dependent on the CTS, and DSR lines being true to
communicate.
The logic analyzer uses the following connections on its RS-232C interface for
three-wire communication:
•Pin 7 SGND (Signal Ground)
•Pin 2 TD (Transmit Data from logic analyzer)
•Pin 3 RD (Receive Data into logic analyzer)
The TD (Transmit Data) line from the logic analyzer must connect to the RD
(Receive Data) line on the controller. Likewise, the RD line from the logic
analyzer must connect to the TD line on the controller. Internal pull-up
resistors in the logic analyzer assure the DCD, DSR, and CTS lines remain
high when you are using a three-wire interface.
Extended Interface with Hardware Handshake
With the extended interface, both the software and the hardware can control
the data flow between the logic analyzer and the controller. This allows you
to have more control of data flow between devices. The logic analyzer uses
the following connections on its RS-232C interface for extended interface
communication:
Programming Over RS-232C
Minimum Three-Wire Interface with Software Protocol
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