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12.3.5 Process input data
The RS232-module sends the data, received by the device, into a 128-byte receive-buffer. The mod-
ule then transmits the data segmented via the module bus and the gateway to the PLC.
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.
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
Status byte
n n + 7
STAT TX_CNT_ACK RX_CNT RX_BYTE_CNT
Diagnostics
n + 1 n + 6 Buf_
Ovfl
Frame
_ERR
HndSh
_ ERR
HW_
Fail
PRM_
ERR
reserved TXBuf-
NotEm
pty
Data bytes
n + 2 n + 5
RX_data byte 0
n + 3 n + 4
RX_data byte 1
n + 4 n + 3
RX_data byte 2
n + 5 n + 2
RX_data byte 3
n + 6 n + 1
RX_data byte 4
n + 7 n
RX_data byte 5
Designation Value Description
STAT 0-1 1: The communication with the data terminal equipment (DTE) is not
disturbed.
0: The communication with the data terminal equipment (DTE) is dis-
turbed.
A diagnostics message is sent only if the parameter ”Deactivate diag-
nostics = no/0“. The diagnostic data show the cause of the communi-
cation disturbance.
The user has to set back this bit in the process output data by using
STATRES.
TX_CNT_ACK 0-3 The value TX_CNT_ACK is a copy of the value TX_CNT. The value
TX_CNT was transferred together with the last data segment of the
process output data.
The value TX_CNT_ACK is a confirmation of successful acceptance of
the data segment using TX_CNT.
RX_CNT 0-3 This value is transferred together with every data segment. The
RX_CNT values are sequential:
00->01->10->11->00…(dezimal: 0->1->2->3->0…)
Errors in this sequence show the loss of data segments.
RX_BYTE_CNT 0-7 Number of the valid bytes in this data segment.
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