Modbus slave Component problem

[p.erasmus]

Hi Ben /leigh.

I am working on a Modbus slave however I have a problem in understanding the GetLastIncoming() macro

First this macro is not in the wiki

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secondly it seems it can index 4 bytes (0-3 shown in the parameters) and it returns a number

I assume the returned number is how many bytes was read from the Incoming transaction,
so if the master send Slave Address ,Command action(read coils etc) and Address of the command action it would return value 3 and the macro will have data in index 0, index 1 and index 2

my issue is now how to access the index bytes ?
please help me understand this it is quite urgent Please

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[BenR]

Hi Peter,

The GetLastIncoming macro is fairly new and allows you to see what the last incoming command from the master was. This allows you to action a change as it happens rather then having to poll all the various modbus registers and locations for a change.

An index value of 0 returns if the last command was a read or write command.
Index value of 1 returns the memory type that was accessed.
Index value of 2 returns the address within the memory type.
Index value of 3 returns the value that was read/written.

The GetLastIncoming only works for singluar values so if the master read/wrote a number of variables at once then the GetLastIncoming will only return the first value/address. We could maybe add a new index 4 to return the number of registers accessed if this would be useful.

[p.erasmus]

never mind