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D-2 ADAM-5000
How to Use the Checksum Feature
A checksum helps you to detect errors in commands from the host to
the modules, and in responses from the modules to the host. The
feature adds two extra checksum characters to the command or
response string, which does reduce the throughput.
D.1 Checksum Enable/Disable
To enable configuration of a module’s checksum feature, its INIT*
terminal should be shorted to its GND terminal, after which the module
should be rebooted. The checksum feature is enabled by setting bit 6
of the data format/checksum parameter to 1. To disable the checksum,
set the parameter to 0. Remember that when using the checksum
feature, it should always be enabled for all connected devices includ-
ing the host computer.
The checksum is represented by a 2-character ASCII hexadecimal
format and is transmitted just prior to the carriage return. The check-
sum equals the modulo-256 (100h) sum of all the ASCII values in the
command preceding the checksum. If the checksum in a command is
missing or incorrect the module will not respond.
Example 1
The following is an example of an Analog Data In command and
response when the checksum is enabled:
Command: #05S10C(cr)
Response: +3.56719D(cr)
The input value at the module in slot 1 of the ADAM-5000 systems at
address 05h is +3.5671 V. (The date format is engineering units.) The
command checksum (0Ch) is the sum of the ASCII values of the
following characters: #, 0, 5, S and 1. The response checksum (9Dh) is
the sum of the ASCII values of the following characters: “>” “+” “3”
“4” “5” “6” “7” and “1”