The WRITE ASCII MESSAGE command is used to start running a write message on the module, that is, putting ASCII characters to the output/transmit buffer of a serial port.
To start a message, the module needs to know the following:
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The port number to be used
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The starting module register number for the data that is processed
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The message number to run
In addition to starting a message, this command is capable of transferring up to nine registers of data from the controller to the module before the message has started (this is the data count). The data sent is stored starting at the start register number provided in Command Word 1.
This command is executed only the first time it is received. To execute the command again, Command Words 0, 1, or 2 (plus any data word that is sent - keyed off the data count) need to be changed. This is done so that the same message does not get continuously run until Command Word 0 changes to a command other than WRITE ASCII MESSAGE.
NOTE: Words 3 through 10 for Command 2 return a 0.
