We are working on the fieldbus applications in various industries, in master/Slave communication. Now, the work is on the response time analysis.

We have some questions, may you be kind to answer it:
1. Do you know any source for information on low priority acyclic messages in Profibus DP? Actually, we have those data for high and low priority acyclic and cyclic messages, but not on low priority acyclic.

2. The response time for Profibus DP high priority acyclic data is about 0.4 [ms], where, in Interbus, the parameter messages take a couple of 10 [ms], which don?t makes sense in terms of comparison.

The question is:
Are Profibus DP high priority acyclic data response time and Interbus parameter messages response time peer comparable, or they are different in the nature, and we can not compare them together?

If so, which parameters of Profibus DP high priority acyclic data and Interbus parameter messages do you suggest to be compared as a peer comparable measure of two fieldbuses, in order to compare their response time?

 

>We are working on the fieldbus applications in various industries,
>in master/Slave communication. Now, the work is on the response time analysis.
>
>We have some questions, may you be kind to answer it:
>1. Do you know any source for information on low priority acyclic
>messages in Profibus DP? Actually, we have those data for high and
>low priority acyclic and cyclic messages, but not on low priority acyclic. <

Acyclic messages exchange happens after every cyclic polling of all slaves. That defines the maximum of the response time. AFAIK ... there is also no prioritized processing of cyclic and acylic messages in the DP protocol.

>2. The response time for Profibus DP high priority acyclic data is
>about 0.4 [ms], <

I'm not convinced about that value... the response time depends on the current transmission speed and the number of active slaves, which defines the duration of the actual cyclic bus polling.

> where, in Interbus, the parameter messages take a couple of 10
> [ms], which don?t makes sense in terms of comparison. <

No, that's not correct... the bus cycle of an Interbus configuration with 5 slaves is round about 2ms. BTW, you can only compare similar bus configurations with an equal
number of slaves...

>The question is:
>Are Profibus DP high priority acyclic data response time and
>Interbus parameter messages response time peer comparable, or they
>are different in the nature, and we can not compare them together? <

IMHO... they are comparable because of both are depending on the cyclic bus polling.

>If so, which parameters of Profibus DP high priority acyclic data
>and Interbus parameter messages do you suggest to be compared as a
>peer comparable measure of two fieldbuses, in order to compare their
>response time? <

You could compare DPV1 messages of Profibus DP with PCP messages of the Interbus.

Best Regards
Armin Steinhoff