COMMERCIAL IN CONFIDENCE
Page 17
Writing the Setpoint
Writing to the CAL Controller requires a three stage process which prevents simultaneous access from
the front panel. To prevent accidental changes caused by unreliable communications, a sequence of
messages must be sent in strict order.
1. Lock the keypad - a sequence referred to as
enter program mode
2. Write new values to the CAL Controller
3. Unlock the keypad and restart with the new values - a sequence referred to as
exit program
mode
1. Enter Program Mode
To enter the programming mode of the CAL Controller, two messages must be transmitted - both must
be recognised, in strict sequence, as valid for the operation to be successful. The first message
informs the controller that the
next
message is a security locking message, if the second message is
not acknowledged correctly, the whole sequence must be re-started from message 1.
1st Message:
byte 0 :
Slave address
xx
byte 1 :
Function code
(write register)
06 hex (always)
byte 2 :
Register Address high byte
03 hex (always)
byte 3 :
Register Address low byte
00 hex (always)
byte 4 :
Register Value high byte
00 hex (always)
byte 5 :
Register Value low byte
05 hex (always)
byte 6 :
CRC low byte
??
byte 7 :
CRC high byte
??
The controller should reply with an identical response, if not, this message should be re-
transmitted until the response is correct.
Note: the 9500 does not require the security message to be sent.
2nd Message:
byte 0 :
Slave address
xx
byte 1 :
Function code
(write register)
06 hex (always)
byte 2 :
Register Address high byte
15 hex (always)
byte 3 :
Register Address low byte
00 hex (always)
byte 4 :
Register Value high byte
00 hex (always)
byte 5 :
Register Value low byte
00 hex (always)
byte 6 :
CRC low byte
??
byte 7 :
CRC high byte
??
The CAL Controller should reply with an identical response, if not, the message pair is lost and
the sequence must be repeated from message 1.
