Scan rate of PAC and C-Bus

What is the max scan time for C-bus. Similarly, what is the maximum scan rate for the PAC (or what ever you want to call it).

I have an application where I want to monitor some inputs that toggle at various stages at around 2-3Hz and at one point at around just under 10Hz.

Can a PAC scan at this rate and will C-bus actually pick up this "faster" input. I am using an Aux input to connect this up (Garage door for those interested)

Mick

 

There is no such thing as a "scan time" on C-Bus. Devices are not polled. When a group address changes, the new state is broadcast to all units in a network. Are you proposing trying to change a group address at 10Hz ? If so, it will not work as you will flood C-Bus with commands.

The PAC runs its logic 5 times per second, if that is what you want to know.

 

Thanks Darren

Thats exactly what I wanted to know. I should have known the answer myself in hindsight.

It would be nice if the PAC (or a similar device) had digital I/O to handle the higher speed stuff like this, but I deal without out it OK

Mick

 

The actual bus speed in Wired C-Bus allows for a single ON or OFF command from a unit to be transmitted in 24ms. The command will be responded to within 16ms of reception by another C-Bus unit(another message can be started to be received during this 16ms latency so it does not need to be taken into account in determining network capacity).

At regular intervals, the C-Bus system conducts a status collection frame for each Application existing on the network (other than Control Trigger and some other special applications), and this status collection message ties up the bus for a maximum period of 150ms. The rate at which this status collection frame is broadcast is programmable over a range from 1 second to 255 seconds between each status collection message with a default rate of 3 seconds per message.

If you have only a single Application (lighting, typically), then with the default status collection message rate, the absolute maximum message rate will be around 39 commands per second. As Darren says, this will "flood" the bus, which is ok for a short burst, but communication (from a bus coupler or similar) at this rate for any length of time will limit the usefulness of the bus for anything else. Note that there are mechanisms that C-Bus units can use to get more out of the bus, but in your application, it sounds like these mechanisms aren't likely to be used.

Don