TE Technology TC-48-20 - Manual (Page 49)

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II. Examples:
A) Send the set temperature of 10.0 to the controller.
1. The control command, CC, for “DESIRED CONTROL TEMPERATURE (SET TEMPERATURE)” is
1c.
2. Multiply the desired set‐point temperature by 10 (10.0
10
x 10
10
= 100
10
).
3. Convert 100 decimal to hexadecimal (64
16
) and add on leading zeros to make the eight‐
character send value DDDD (0064).
4. Compute the checksum (SS) by adding the hexadecimal values of the following ASCII
characters: 1, c, 0, 0, 6, and 4:
ASCII Character: Hexadecimal Value:
1 31
c 63
0 30
0 30
6 36
4 34
Sum 15e
16
The 8‐bit checksum is the 8 least significant binary bits of the sum, represented as 5e in
hexadecimal.
5. Combining all of these characters in one string we send: (stx)1c00645e(etx).
6. If the temperature controller receives the command and the checksum is correct, it will send
back: (stx)0064ca(ack). If the checksum is not correct the temperature controller will send
back: (stx)XXXX60(ack).
B) Send the set temperature of ‐1.5 °C.
1. The controller command, CC, is by definition 1c.
2. Multiply the desired set‐point temperature by 10
10
(‐1.5 x 10 = ‐15).
3. Convert ‐15
10
to hexadecimal by taking the two’s complement of the number. (This can be
easily done by using the formula 2 n – N, where n is the word‐bit size and N is the absolute
value of the number being converted.) Hence, you have 2 16 ‐ 15 = 65521
10
. This value then
converts to fff1
16
.
4. Compute the checksum (SS) by adding the hexadecimal ASCII values of the following
characters: 1, c, f, f, f, 1,:
ASCII Character:
Hexadecimal Value:
1 31
c 63
f 66
f 66
f 66
1 31
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)1cfff1f7(etx).
6. If the temperature controller receives the command and the checksum is correct, it will send
back: (stx)fff163(ack). If the checksum is not correct the temperature controller will send
back: (stx)XXXX60(ack).
C) Read the actual temperature of the control thermistor.
1. Let us assume the actual temperature is 2.5 °C
2. The control command, CC, for “CONTROL 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