Technology Modules
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12.3 RS232 interface – BL20-1RS232
The module BL20-1RS232 transmits serial data through the BL20 system via a RS232 interface and
enables the connection of different devices (printer/ scanner/ bar code reader), which as well pro-
vide a serial RS232 interface.
12.3.1 Data transfer method
The RS232-module enables flexible serial data transfer. An operational data transfer method can be
set by the module’s parameters.
The data transfer can be parameterized as follows:
Data rate: 300…115200 bps.
Data bits: 7 or 8 data bits in one data frame
Parity: none, odd or even
Stop bits: 1 or 2 bit.
12.3.2 Data exchange
For the data exchange with a field device, the RS232-module provides a 64-byte transmit-buffer and
a 128-byte receive-buffer. This is a hardware-restriction. The data telegrams which have to be sent
or received can be larger.
The data transfer from the PLC into the transmit-buffer of the module or from the receive-buffer of
the
module to the PLC is realized via a 8-byte transmission channel in the Process output data (page
400)or Process input data (page 398).
To ensure the error-free data transmission, 2 byte of each data package are used to display status-,
control- and diagnosis information. The amount of user data is therefore reduced to 6 byte within a
data package
Fig. 275: BL20-1RS232
NOTE
The data flow control can be realized via a hardware handshake (RTS/CTS) or a software
handshake (XON/XOFF).
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