Sending Commands, Chapter 4
Data Communications with the Watlow Series 988 Family
4.9
Exception Responses
When a controller cannot process a command it returns an exception response and
sets the high bit (0x80) of the command.
0x01 illegal command
0x02 illegal data address
0x03 illegal data value
Packet returned by controller: | nn | nn | nn | nn nn |
∆
∆
∆
∆ ∆
controller address (one byte)
c 0x80
exception code (0x01 or 0x02 or 0x03)
CRC low byte
CRC high byte
Messages with the wrong format, timing or CRC are ignored. A read command sent
to an inactive parameter returns 0x0000.
Example: Exception 01 - Command 02 is not supported.
Sent:
01 02 00 01 00 02 A8 0B
Received:
01 82 01 81 60
Example: Exception 02 - The parameter at register 45 (0x002D) is inactive.
Sent:
01 06 00 2D 00 01 D8 C3
Received:
01 86 02 C3 A1
Example: Exception 03 - Cannot write 12,000 (0x2EE0) to register 7, out of range,
illegal data value.
Sent:
01 06 00 07 2E E0 24 23
Received:
01 86 03 02 61
Commands
