ASCII Character: Hexadecimal Value:
1 31
c 63
f 66
f 66
6 36
a 61
Sum 1f7
16
The 8-bit checksum is the 8 least significant binary bits of the sum, represented as f7 in hexadecimal.
5. Combining all of these characters in one string we send: (stx)1cff6af7(etx).
6. If the temperature controller receives the command and the checksum is correct, it will send back:
(stx)ff6a63(ack). If the checksum is not correct the temperature controller will send back:
(stx)XXXX60(ack).
D) Read the actual temperature of the control thermistor.
1. Let us assume the actual temperature is 2.50 °C.
2. The control command, CC, for “INPUT1” sensor temperature is 01.
3. There is no send value, so we calculate the checksum (SS) by adding the ASCII values of the characters
0, 1, 0, 0, 0, 0:
ASCII Character: Hexadecimal Value:
0 30
1 31
0 30
0 30
0 30
0 30
Sum 121
16
The 8-bit checksum is the 8 least significant binary bits of the sum, represented as 21 in
hexadecimal.
4. Combining the characters in one string we send: (stx)01000021(etx).
5. If the temperature controller receives the command and the checksum is correct, it will send back:
(stx)00fa27(ack). The “27” at the end of the string is the checksum of “00fa”. The value 00fa
16
converts to 250
10
. This number, when divided by 100, is 2.50--the temperature in °C. As in the other
examples, if the controller did not calculate the correct checksum from the query it would send back:
(stx)XXXX60(ack).
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