FX3U and FX5U Modbus RTU comparison

[Clear.Mind 18]

Hello. I have tested different type of communication between by rs485 fx3u and fx5u.
On fx3u side used fx3u-485-adp-mb.
In case of N:N and Parallel Link fx5u is more comfortable than fx3u. But, modbus rtu not so good.
I made 3 tests:

1)FX3u master with ADPRW function;
ADPRW in fx3u supports wider count of modbus functions, most usefull for me is H17 (Read/Write multipleregisters). But when i send telegram to Fx5u with this function, fx5u fall in error (recieved unsupports serial com functions).

i have checked instruction manual on ADPRW - FX5u doesn't support H17, only H03 and H10. For read/write from fx5u need to use 2 instructions on FX3u side.

2)FX5u master with ADPRW function;
In this test ofcourse i tried use H17, but result was expected - error.

3)FX5u master with predifined protocol.
In this test using H17 function on Fx5u side was successful.

Conclusion: FX5u better use as master for modbus rtu communications via predifined protocols, and if it used as slave need remember that it doesn't support H17.

I hope this information will usefull for sombody.

[eziccc 1]

Hi Clear.Mind! When using fx5u as master - do you know where to find each slave status? sm8500 ? Thnx.

[Clear.Mind 18]

On 21.08.2017 at 7:36 PM, eziccc said:

Hi Clear.Mind! When using fx5u as master - do you know where to find each slave status? sm8500 ? Thnx.

Yes, you can check sm8500 status after completation of instruction, but I have used binary output array of completation status of ADPRW or S_CPRTCL. (Head device number which turns ON when the execution of the instruction is completed and remains on for 1 scan.If the instruction is completed with an error, (d)+1 is alsoturned on.)