turck BL20 Series - 12.4.7 Process output data

413
2020/09
12.4.7 Process output data
The data received from the PLC are loaded into a transmit-buffer in the BL××-1RS485/422 module.
The transmission is realized in a 8-byte format which is structured as follows:
 1 control byte is required to ensure trouble-free transmission of the data.
 1 byte contains signals to start the flushing of transmit- and receive buffer.
 6 bytes are used to contain the user data.
n = offset of input data; depending on extension of station and the corresponding fieldbus.
Byte Byte
DP/PN
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Control byte
n n + 7 STATR
ES
RX_CNT_ACK TX_CNT TX_BYTE_CNT
Flushing of receive- or transmit-buffer
n + 1 n + 6 reserved TXBuf-
Dis
RXBUF
FLUSH
TXBUF
FLUSH
Data bytes
n + 2 n + 5 TX_data byte 0
n + 3 n + 4 TX_data byte 1
n + 4 n + 3 TX_data byte 2
n + 5 n + 2 TX_data byte 3
n + 6 n + 1 TX_data byte 4
n + 7 n TX_data byte 5
Designation Value Description
STATRES 0 - 1 This bit is set to reset the STAT bit in the process input data.
With the change from 1 to 0 the STAT bit is reset (from 0 to 1). The clear-
ing of the receive and transmit buffer by RXBUF FLUSH/TXBUF FLUSH
is possible.
If this bit is 0, all changes in TX_BYTE_CNT, TX_CNT and RX_CNT_ACK
are ignored. The value 1, 0 or the transition from 0 to 1 disables the
clearing of the receive and transmit buffer by the RXBUF FLUSH/TXBUF
FLUSH.
RX_CNT_ACK 0 - 3 The value TX_CNT_ACK is a copy of the value TX_CNT. The value
RX_CNT was transferred together with the last data segment of the
process input data.
The value TX_CNT_ACK is a confirmation of successful acceptance of
the data segment using TX_CNT.
TX_CNT 0 - 3 This value is transferred together with every data segment. The
TX_CNT values are sequential:
0001101100…
(decimal: 01230…)
Errors in this sequence show the loss of data segments.
TX_BYTE_CNT 0 - 7 Number of the valid bytes in this data segment.