Watlow Series 97 - Manual (Page 70)

A . 8 ■ A p p e n d i x Wa t l o w S e r i e s 9 7
Example: Run loop back test on controller at address 40 (0x28).
Sent: 28 08 55 66 77 88 31 B7
Received: 28 08 55 66 77 88 31 B7
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)
command + 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 02 59 2E E0 44 49
Received: 01 86 03 81 82
NOTE: For more information about communicating with Watlow controllers, go to www.watlow.com and download the
Data Communications Reference: Electronic User’s Manual. It is located under Literature, User’s Manuals, English and
search on data communications reference.