Computer Interfacing
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Modbus RTU T1T2T3T4 implementation

How to recognize the intervale between massages in Modbus RTU?


 

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Author Message
Ding
New User



Joined: 16 Jul 2009
Posts: 1


Jul 16, 2009 4:33 am

Hi, I was wondering how to recognize 3.5 character silence interval between two Modbus RTU messages, which is required by Modbus RTU protocal to distinguish two message packets. The interval is about 5ms at 19200 baudrate at serial port. I am using VB 2008.

1. By timer:in VB 2008, the timer is not accurate, and can not handle interval less than 100 ms.

2. By Readbyte event. Each byte received causes an event, and I judege the timespan of each byte received. Unfortunately, after testing, I found the bytes were received too fast to be handled if PC checks and compares each byte arriving timing.

Any body give me a clue on this? Thanks a lot.

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