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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.
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