About sys_pausecom function of the IDK

Product : ISaGRAF 3.x

Date : 26-January-2001

File : About sys_pausecom function of the IDK.htm

Subject : About PAUSECOM constant

Keywords: PAUSECOM - sys_pausecom - communication - IDK

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In the IDK manual, "C3.5 C.3.5 Communication management functions" of

"sys_pausecom" said:

NOTE:

The PAUSECOM constant need to be adapted.

To comply with Modbus, the value must be the duration of 3 characters.

Question:

What does it mean 3 characters?

Answer:

1 char = about 11 bits (start bit / Stop / Parity)

It is used to re-synchronize beginning of frames on a blank (no characters during a certain time that is usually 3 char)

Of course this value must be adapted according the system clock accuracy.

At 600 baud PAUSECOM may be 55ms

At 9600 baud PAUSECOM may be 2.5ms but with a tick at 10ms it is best to have 10ms.

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