Technology modules
D300529 0115 - BL67 I/O modules12-18
12.2 BL67-1RS485/422
The module BL67-1RS485/422 allows the transfer of serial data streams via the RS485/422 interface and
therefore enables various devices to be connected, such as printers, scanners or bar code readers that
use the RS485/422 interface for communication. The interface transfers the data received from the
device to the PLC or transfers data to be sent from the PLC to the device.
12.2.1 Data transfer method
The module enables flexible serial data transfer. The RS422 connection mode supports two wire sim-
plex or four wire full-duplex transmission. The RS485
connection supports two wire half-duplex trans-
mission.
An operational data transfer method ca
n be set by the module’s parameters.
The data transfer can be paramete
rized as follows:
Data rate: 300 bps to 115200 bps
Data bits: 7 or 8 data bits in one data frame
Parity: none, odd or even
Stop bits: 1 or 2 bit.
The data flow control can be implemented in RS422 operation with a software handshake (XON/XOFF)
ro
utine.
12.2.2 Data exchange
For the data exchange with a field device, the 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 th
e transmit-buffer of the module or from the receive-buffer of the
RS485/422 module to the PLC is realized via a 8-byte transmission channe
l in the process output or pro-
cess input data.
To ensure the error-free data transmissio
n, 2 byte of each data package are used to display status-, con-
trol- and diagnosis information. The amount of user data
is therefore reduced to 6 byte within a data
package
12.2.3 Process data
With PROFIBUS, PROFINET and CANopen, the I/O data of this module is localized within the process
data of the whole station via the hardware configuration tool of the fieldbus maste
r.
With DeviceNet, EtherNet/IP and Modbus TCP a detailed mapping table can be created with the
TURCK configuration tool I/O-ASSISTANT (PACTware + BL67-DTM).
Process input data
The RS485/422-module sends the data, received by the device, into a 128-byte receive-buffer. The
module then transmits the data segmented via the module bus and the gateway to the SPS.
The transmission is realized in a 8-byte format which is structured as follows:
1 status byte is required to ensure trouble-free transmission of the data.
1 byte contains the diagnostics data.
6 bytes are used to contain the user data.
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