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Old January 10th, 2016   #2
hamish
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Default 485 IO Interrupt driven buffering

Quote:
Originally Posted by Cyril View Post
Hi

Someone can discuss about the minimal frequence necessary for the mcu ? I code a rdm responder fully fonctionnal but I have to work in 16 MHz but I don't understand why it don't work with 8MHz ...

Thank you

Have a nice day
Cyril
Hi Cyril

Two main factors that determine what clock speed is required to meet the requirements of RDM.

First, IMO, set up interrupt tasks for buffering IO/485 data, thus allowing you to run other processes without missing packet data.
Built in to these interrupt driven task should be the response timing to meet the responder requirements of the standard.

Second, consider how to handle your responses when saving data to non volatile memory. Either you will have to assign the data saving to another task and then respond ahead of the save task completing.
or
Alternatively, (not my preferred answer) employ ACK timer to allow time for the data save to complete before completing a response.

I have a myriad of responder implementations running on an 8MHZ clock, running several other processes with ample resource.

Hope this helps.

Hamish
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