BayTech RPC Single-phase Conbined QS - Manual (Page 35)

RPC with or without Ethernet
34
Handshaking
For a simple communication between modems three connected lines are needed: TX, Rx, and Ground.
For the data to be transmitted, both sides have to be clocking the data at the same baud rate. While this
method is sufficient for most applications, it is limited in being able to respond to problems such as the
receiver getting overloaded. This is where serial handshaking can help.
Select 1), for the Handshaking menu, Default is None, the RPC display with the following:
Type the number of the handshaking option and press .
1. Software Handshaking: This style uses actual data bytes as control characters. The lines
necessary are TX, Rx, and ground since the control characters are sent over the transmission
line like regular data. The two control characters, XON and XOFF are characters sent by the
receiver of the data to halt the transmitter during communication.
2. NOTE: A drawback to this method is also the most important fact to keep in mind. In ASCII
transmissions these character values are non-character values; however, data being transmitted
via binary, it is very likely that these values could be transmitted as data and the transmission
would fail.
3.
Hardware Handshaking: This style uses actual hardware lines. Like the TX and Rx lines, the
RTS/CTS and DTR/DSR lines work together. When a receiver is ready for data, it will assert
the RTS (Request to Send) line. This is then read by the sender at the CTS (Clear to Send)
input, indicating it is clear to send the data. DTR (Data Terminal Ready) and DSR (Data Set
Ready) allow the serial port and the modem to communicate their status. When the modem is
ready for data to be sent, it will assert the DTR line indicating that a connection has been made
across the phone line. This is read in through the DSR line and the modem can begin to send
data. The general rule of thumb is that the DTR/DSR lines are used to indicate that the system
is ready for communication where the RTS/CTS lines are used for individual packets of data.
+----+------+-----------------+------+------+------+------+---------+----+----+
|Port|Device| Device | Baud | Word | Stop |Parity|Handshake|LineDrive|
| | Type | Name | Rate | Size | Bits | | |DTR |RTS |
+----+------+-----------------+------+------+------+------+---------+----+----+
| 1 | RS232| EIA-RS232 | 9600 | 8 | 1 | None | None | HI | HI |
+----+------+-----------------+------+------+------+------+---------+----+----+
Handshaking......................1
Baud Rate........................2
Word Size........................3
Stop Bits........................4
Parity...........................5
RTS Line Driver Inactive State...6
DTR Line Driver Inactive State...7
Enter Request :1
Select handshaking:
1 For None
2 For Software Handshaking
3 For Hardware Handshaking
Enter Request :