Exceptions; Crc; Device Compatibility Parameters - Control Techniques Digitax ST Advanced User's Manual

Parameter Keypad and
structure display
Start Number
Read register of 16bit
address registers
#1.28 127 1
#1.28 16511* 2
#1.28 16511* 1
#1.29 128 1
#1.29 16512* 2
#1.30 16513* 2
#1.28
- 127 2
#1.29
#1.28
- 16511* 4
#1.29
*Bit 14 is set to allow 32 bit access
Writes when actual parameter type is different from
selected
The slave will allow writing a 32 bit value to a 16 bit parameter as long as
the 32 bit value is within the normal range of the 16 bit parameter.
The slave will allow a 16 bit write to a 32 bit parameter. The slave will
sign extend the written value, therefore, the effective range of this type of
write will be ±32767.
Examples, if #1.28 has a range of ±100000, and #1.29 has a range of
±10000.
Start Number
Write register of 16bit
address registers
#1.28 127 1
#1.28 127 1
#1.28 16511* 2
#1.29 128 1
#1.29 16512* 2
*Bit 14 is set to allow 32 bit access
6.2.8

Exceptions

The slave will respond with an exception response if an error is detected
in the master request. If a message is corrupted and the frame is not
received or the CRC fails then the slave will not issue an exception. In
this case the master device will time out. If a write multiple (FC16 or
FC23) request exceeds the slave maximum buffer size then the slave
will discard the message. No exception will be transmitted in this case
and the master will time out.
Digitax ST Advanced User Guide
Issue Number: 1
Parameter description
Parameter x.00
format
Response Comments
Standard 16 bit access
to a 32bit register will
0x5678
return low 16bit word of
truncated data
0x12345678 Full 32bit access
Number of words must
Exception 2
be even for 32bit access
Standard 16 bit access
to a 32bit register will
0xABCD
return low 16bit word of
data
32bit access to a 16bit
0xFFFFABCD register will return 32bit
sign extended data
32bit access to a 16bit
0x00000123 register will return 32bit
sign extended data
Standard 16 bit access
0x5678, to a 32bit register will
0xABCD return low 16bit word of
truncated data
0x12345678,
Full 32bit access
0xFFFFABCD
Data Comments
Standard 16 bit write to a
0x1234 32bit register. Value
written = 0x00001234
Standard 16 bit write to a
0xABCD 32bit register. Value
written = 0xFFFFABCD
Value written =
0x00001234
0x00001234
0x0123 Value written = 0x0123
Value written =
0x00000123
0x00000123
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Advanced parameter Serial comms
descriptions protocol
Exception message format
The slave exception message has the following format.
Byte
0 Slave source node address
1 Original function code with bit7 set
2 Exception code
3 CRC LSB
4 CRC MSB
Exception codes
The following exception codes are supported.
Code
1 Function code not supported
Register address out of range, or request to read too many
2
registers
Parameter over range during block write FC16
The slave processes the write block in the order the data is received. If a
write fails due to an out of range value then the write block is terminated.
However, the slave does not raise an exception response, rather the
error condition is signalled to the master by the number of successful
writes field in the response.
Parameter over range during block read/write FC23
There will be no indication that there has been a value out of range
during a FC23 access.
6.2.9

CRC

The CRC is a 16bit cyclic redundancy check using the standard CRC-16
polynomial x16 + x15 + x2 + 1. The 16bit CRC is appended to the
message and transmitted LSB first.
The CRC is calculated on ALL the bytes in the frame.
6.2.10

Device compatibility parameters

All devices have the following compatibility parameters defined:
Parameter
Device ID
Minimum slave response
time
Maximum slave response
time
Maximum baud rate
32bit float data type
supported
Maximum buffer size
Electronic
Performance
nameplate
Description
Description
Description
Unique device identification code
The minimum delay between the end of a
message from the master and the time at
which the master is ready to receive a
response from the slave.
Refer to Pr 11.26
When global addressing, the master
must wait for this time before issuing a
new message. In a network of devices,
the slowest time must be used
115, 200
If this data type is not supported then an
over range error will be raised if this data
type is used
Determines the maximum block size.
215