Technical data

36 Function Description WAGO-I/O-SYSTEM 750
750-652 Serial Interface RS-232 / RS-485
Manual
Version 1.3.0
The time period after which the I/O module starts data transmission can be
defined using the "Continuous Receive Timeout" parameter. Because the duration
of the transfer of any amount of data depends on the baud rate setting, number of
data and stop bits and the parity, an absolute time specification is not feasible.
Therefore, the time required to transmit exactly one character to the serial
interface in the current interface parameter setting is used as the unit of
measurement.
5.1.3 RS-232 Operating Mode
The RS-232 operating mode in full-duplex is realized in a 2-wire or 4-wire point-
to-point connection. Simultaneous transmission and receiving is possible.
In this mode, the I/O module supports flow control for the serial interface. The I/O
module can be set, so that flow control occurs using of one of the following
methods:
• XON-/XOFF protocol
• RTS/CTS
• RTS/CTS, RTS with lead / follow-on time (firmware version 03 or higher)
5.1.3.1 Flow Control Using XON-/XOFF Protocol
If flow control is activated using XON-/XOFF protocol, the I/O modules stops
transmitting data to the serial interface when it receives the XOFF character
(DC3==0x13) from the serial device. The I/O module continues transmitting data
when it receives the XON character (DC1==0x11). When data is received, the I/O
module monitors input buffer usage. It transmits the XOFF control character to
the serial device when the number of characters in the input buffer exceeds 2304.
If the number of characters in the input buffer is below 2176, it transmits XON.
5.1.3.2 Flow Control Using RTS/CTS
If flow control is activated using RTS/CTS, the I/O module stops transmitting
data to the serial interface when CTS is set. The I/O module continues
transmitting data when CTS is reset. When data is received, the I/O module
monitors input buffer usage. It sets RTS when the number of characters in the
input buffer exceeds 2304. If the number of characters in the input buffer is below
2176, the I/O module resets RTS.