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How to use the Checksum feature
F-
2
ADAM 4000 Series User’s Manual
A checksum helps you detect communication errors between the host
and module. This feature adds two extra checksum characters to the
command or response string; therefore, it reduces the throughput.
F.1 Checksum Enable/Disable
In order to enable configuration of a module’s checksum feature, its
INIT* terminal should be shorted to its GND terminal. Then, the
module should be rebooted. The checksum feature is enabled by setting
bit 6 of the data format/checksum parameter to 1. On the other hand,
the checksum is disabled by setting the parameter to 0. Whenever the
checksum feature is used, all the connected devices including the host
computer should be in enable mode.
The checksum is represented by a 2-character ASCII hexadecimal
format and is transmitted just prior to the carriage return. The checksum
equals to the result after performing modulus-256 (100h) of all the
ASCII values’ sum preceding the checksum. If the checksum is missing
or incorrect, the module will not respond.
Example 1
The following example is an Analog Data In command and response
when the checksum is enabled:
Command: #0588(CR)
Response: +3.56719D(CR)
The input value of the module at address 05h is +3.5671 V. (The data
format is in engineering units.) The command checksum (88h) is the
sum of the ASCII values for the following characters: #, 0, and 5. The
response checksum (9Dh) is the sum of the ASCII values for the
following characters: “>”, “+”, “3”, “.”, “5”, “6”, “7”, and “1”.