turck BL20 Series - 12.5.6 Signal types - Pin assignment SSI; 12.5.7 Process input data

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12.5.6 Signal types – Pin assignment SSI
12.5.7 Process input data
The field input data is transferred from the connected field device to BL20-1SSI-module.
The process input data is the data that is transferred to the PLC from the BL20-1SS1 via a gateway.
The transmission is realized in a 8-byte format which is structured as follows:
 4 bytes are used for representing the data that was read from the register with the address stated
at REG_RD_ADR.
 When necessary, 1 byte represents the register address of the read data and an acknowledgment
that the read operation was successful.
 1 byte can be used to transfer status messages of the SSI encoder. This byte also contains an
acknowledgment that the write operation to the register was successful and indication of an
active write operation.
 1 byte contains the results of comparison operations with the SSI encoder value.
 1 byte contains messages concerning the communication status between the BL20-1SSI module
and the SSI encoder, as well as other results of comparison operations.
The following table describes the structure of the 8 × 8 bits of the process input data.
STS (or ERR) contains non-retentive status information, i.e. the bit concerned indicates the actual
status.
FLAG describes a retentive flag that is set in the event of a particular event. The bit concerned retains
the value until it is reset.
Signal designation
CL Clock
D Data
GND Ground
Byte Byte
DP/PN
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Diagnostics
n n + 7 STS_STOP - - ERR_
PARA
STS_
UFLW
STS_
OFLW
ERR_
SSI
SSI_DI
AG
Status messages SSI
n + 1 n + 6 STS_UP STS_DN REL_
CMP2
FLAG
CMP2
STS_
CMP2
REL_
CMP1
FLAG
CMP1
STS_
CMP1
n + 2 n + 5 REG_WR_
ACEPT
REG_
WR_AKN
- - SSI_S
TS3
SSI_S
TS2
SSI_S
TS1
SSI_S
TS0
n + 3 n + 4 REG_RD_
ABORT
- REG_RD_ADR
Data bytes
n + 4 n + 3 REG_RD_DATA, data byte 0
n + 5 n + 2 REG_RD_DATA, data byte 1
n + 6 n + 1 REG_RD_DATA, data byte 2
n + 7 n
REG_RD_DATA, data byte 3