Satec EM133, Reference Manual

Page: 9 / 340

9
Device Response Block
The device response block size can vary from 6 to 32 bytes. The device response block
formats are shown in Tables 2-5 and 2-6.
Successful read and write are acknowledged by the retransmission of bytes 0-3 of the
master request. Negative response is acknowledged by the retransmission of bytes 0-3 of
the master request with a non-zero exception code in byte 1. Note that the scaling bit in
byte 0 may be dropped if there is actually no scaled data in the response message.
Table 2-5 Read Response Block
Bytes Description Range Type Notes
0,1 Response control See Table 2-7 UINT16
2,3 Start point ID 0x0000-0Xffff UINT16
4-31 Data block INT16/INT
32 32-bit integers occupy two
16-bit words
– most
significant first
Table 2-6 Write Response Block
Bytes Description Range Type Notes
0,1 Response control See Table 2-7 UINT16
2,3 Start point ID 0x0000-0xFFFF UINT16
4-31 Unused 0
Table 2-7 Response Control
Byte Bits Description Range Notes
0 0-1 Operation 00=data is not valid
01=read
10=write
11=data is not valid
“Data is not valid“ indicates that the data in the
device response block is not reliable and should
not be concerned
2 Data type 0=32-bit integer
1=16-bit integer
32-bit integers occupy two 16-bit words – most
significant first
3 Unused 0
4 16-bit linear
scaling
0=no scaling
1=scaled data
Only 16-bit analog registers are affected. Binary
registers and counters are not scaled.
5-6 Unused 0
7 Synchronization
bit 0-1 Synchronized with the master synchronization
bit when command handling is completed
1 0-3 Word count 0-14 Indicates the number of words in the data block
4-7 Exception code See Table 2-8
Note: Bit 0 is a least significant bit (LSB).
Table 2-8 Exception Codes
Code Exception Cause Notes
0 No exception
1 Illegal
operation The requested operation is not allowed for the
point The request is discarded
2 Illegal
address
1. Start point ID points to an inexistent point
2. The number of requested points exceeds the
actual number of points available
3. Uneven word count with 32-bit data type
The request is discarded
3 Illegal data Written data is out of the allowable range The request is discarded
4 Over-range
error The requested data cannot be transmitted using
16-bit data type The request is handled with
over-ranged points being
truncated to a maximum
allowable 16-bit negative or
positive number.
The operation field in the device response indicates that the data in the response block is
valid and can be handled by the master. The master should not concern the data in the
device response block if this field contains an invalid code, or the exception field contains
a non-zero value.
The following table describes the mapping between TPDOs and data bytes sent by the
EM133: