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5.1
Serial Communication Interface Programming
TIM-100/120 Normal Acknowledgment
For both pressure and flow set point commands, the TIM-100/120 responds with the following
acknowledgment.
TIM-100/120 to Host Response:
>A1xxxyy
↵
Where:
xxx = 000 to FFF representing a 0 to full scale range
yy = two hex character check sum
Function:
This response indicates an acknowledgement with data but without error.
TIM-100/120 Error Response
An error response begins with the character “N” followed by the error code and carriage return
“
↵
”. It does not require a checksum. Error codes are listed in Appendix C.
Calculating End of Message Checksum
All command messages end with two ASCII-hex digits representing the message checksum,
followed by a carriage return. The checksum is computed by (a) adding the decimal values of
all the ASCII characters in the message, excluding the start of command character, ">", (b)
dividing the sum by 256 and (c) converting the integer remainder to a two ASCII-hex digits.
Example:
•
Command: >08K012
‚
Ignore the ">" character
ƒ
Convert the remaining characters to decimal values
Character
Hex Value
Decimal Value
0
30
48
8
38
56
K
4B
75
0
30
48
1
31
49
2
32
50
SUM
146
326
„
Divide the sum by 256:
326/256 = 1 remainder 70
…
Convert the remainder to a two ASCII-hex digits:
70 decimal = 46 hex
Note:
•
Notice that 46 are only the
last two digits
in the hex sum.
•
Therefore, the checksum in this example is 46.
†
The complete command is written as:
>08K01246
↵
Note:
•
Although not recommended, the checksum can be replaced by the
wildcard symbol “??”.The use of the wildcard symbol does not verify the
message integrity.
