TE Technology TC-24-25 - Manual (Page 23)

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If the checksum for a command or query is not correct the temperature controller will respond with eight
upper case X’s and then c0, which is the checksum of these eight X’s:
(stx)XXXXXXXXc0(ack)
Remember, AA = 00 is the universal address, and all controllers will respond (be careful!). If JP1-6 is
jumped to JP1-3 when powered, then the controller’s address will be 63 hex (used to setup newly added
controller to the serial link). If the address is not correct or not as listed immediately above then the
controller will not respond to any requests.
II. Examples:
Set the controller at address 01 to control via a computer programmable set point.
1. The controller address, AA, is by definition 01.
2. The control command, CC, for “INPUT2 DEFINE” is 29 hex.
3. A data value of “0” selects a computer communicated set value, so the eight-character send
value DDDDDDDD is 00000000.
4. Compute the checksum (SS) by adding the ASCII values of the following characters: 0, 1, 2,
9, 0, 0, 0, 0, 0, 0, 0, and 0:
ASCII Character:
Hex Value:
0 30 hex
1 31 hex
2 32 hex
9 39 hex
0 30 hex
0 30 hex
0 30 hex
0 30 hex
0 30 hex
0 30 hex
0 30 hex
0 30 hex
Sum 024c hex
The 8-bit checksum is the 8 least significant binary bits of the sum, represented as
4c in hex.
5. Combining all of these characters in one string we send: (stx)0129000000004c(etx).
6. If the temperature controller receives the command and the checksum is correct, it will send
back: (stx)0000000080(ack). If the checksum is not correct the temperature controller will
send back: (stx)XXXXXXXXc0(ack).