Rs232 Handshaking Defined; Rs232 Cable Connectivity; Figure 3-1. Point To Point Architecture Using Rs232; Figure 3-2. Multi-Drop Topology Using Rs232 - ABB TPU2000 Technical Manual

TPU2000/2000R Modbus/Modbus Plus/ Modbus TCP/IP Automation Guide

RS232 Handshaking Defined

Handshaking is the ability of the device to control the flow of data between devices. There are two types of
"handshaking", hardware and software. Hardware handshaking involves the manipulation of the RTS (Request to
Send) and CTS (Clear to Send) card control signal lines allowing data communication direction and data flow
rates to be controlled by the DTE device. Also the flow is controlled by the DTR (Data Terminal Ready) signal
which allows the DCE operation.
Software handshaking involves the data flow control by sending specific characters in the data streams. To
enable transmission, the XON character is transmitted. To disable reception of data, the transmitting device
sends an XOFF character. If the XOFF character is imbedded within the data stream as information, the receiving
node automatically turns off. This is the main weakness of software handshaking, inadvertent operation due to
control characters being imbedded within data streams. Software handshaking is usually used in printer control.
The TPU2000 and TPU2000R devices do not incorporate handshaking, therefore, the control lines may be
ignored as illustrated in Figure 3-3. However, some PC software utilizes handshaking, thus the port on the
personal computer may require a special hardware configuration of the cable to the port. Consult with the
software vendor to determine RS232 control and buffering requirements and the need for signal jumpers required
in RS232 cabling.
The ports on the TPU/TPU/GPU have been tested for operation up to a speed of 19,200 baud. 19,200 baud is
the typical data rate applicable for the operation of an asynchronous communication connection over RS232
without the use of additional timing lines.

RS232 Cable Connectivity

A cable diagram is illustrated in Figure 3-3 and 3-4. Figure 3-3 shows the direction of communication signal
transmission and the gender of the connectors used in constructing a communication cable.
Personal Computer

Figure 3-1. Point to Point Architecture Using RS232

Host
Executing
HM I
Software
or
The Cloud.
ECP

Figure 3-2. Multi-Drop Topology Using RS232

ECP Software
Com 0
E C
TPU2000R
C
E
TPU2000R
C
E
TPU2000R
STATUS
C C E E
TPU2000
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