Device Response Block - Satec EM133 Reference Manual

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
0,1 Response control
2,3 Start point ID
4-31 Data block
Table 2-6 Write Response Block
Bytes Description
0,1 Response control
2,3 Start point ID
4-31 Unused
Table 2-7 Response Control
Byte Bits Description
0 0-1 Operation
2 Data type
3 Unused
4 16-bit linear
scaling
5-6 Unused
7 Synchronization
bit
1 0-3 Word count
4-7 Exception code
Note: Bit 0 is a least significant bit (LSB).
Table 2-8 Exception Codes
Code Exception
0 No exception
1 Illegal
operation
2 Illegal
address
3 Illegal data
4 Over-range
error
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:
Range
See Table 2-7
0x0000-0Xffff
Range
See Table 2-7
0x0000-0xFFFF
0
Range
00=data is not valid
01=read
10=write
11=data is not valid
0=32-bit integer
1=16-bit integer
0
0=no scaling
1=scaled data
0
0-1
0-14
See Table 2-8
Cause
The requested operation is not allowed for the
point
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
Written data is out of the allowable range
The requested data cannot be transmitted using
16-bit data type
Type
UINT16
UINT16
INT16/INT 32-bit integers occupy two
32 16-bit words – most
significant first
Type
UINT16
UINT16
Notes
"Data is not valid" indicates that the data in the
device response block is not reliable and should
not be concerned
32-bit integers occupy two 16-bit words – most
significant first
Only 16-bit analog registers are affected. Binary
registers and counters are not scaled.
Synchronized with the master synchronization
bit when command handling is completed
Indicates the number of words in the data block
The request is discarded
The request is discarded
The request is discarded
The request is handled with
over-ranged points being
truncated to a maximum
allowable 16-bit negative or
positive number.
Notes
Notes
Notes
9