Best Practices and Troubleshooting
46
sysmik.de
Manual SCA-340 / SCA-340-L
5.
Best Practices and Troubleshooting
5.1
Performance and Resource Management
All software processes share the common resources (processor time, memory).
Besides the complexity of the application itself, the interface definitions, especially
the connected I/O terminals have an important impact on ressource usage. While
each data point needs ressources just by its existence, it is usually also processed
within the application, thus enlarging the application.
Note:
All quantitative information given in this chapter are not guaranteed. They may help
you to estimate the load caused by I/O terminals.
I/O terminals
Scalibur can handle up to 63 I/O and function terminals. This is a rather theoretical
limit, which gets relativated by the geometrical size of the station. In general,
stations with more terminals need more time to transfer data between controller and
terminals. Digital input and putput terminals have the least performance impact.
If you connect 63 digital I/O terminals with 32 channels each, the station has 2016
I/O datapoints, while being more than 9 ft. wide. Supply and segment terminals
might enlarge the stations width even further.
IB IL DALI/PWR, IB IL DALI, IB IL DALI/MM
A DALI terminal can adress up to 81 data points (64 short addresses, 16 group
addresses, one broadcast). The ressource demand depends on the number of DALI
ballasts and how they are controlled:
addressing via broadcast (one data point, no status), maybe using scenes
group addressing (some data points, which are written on change only, no
status)
individual addressing (many data points, which are written on change only)
individual addressing with evaluation of ballast status (many data points,
which are polled periodically)
individual or group addressing with additional use of DALI sensors
While e.g. broadcast addressing needs little ressources and would allow the
maximum number of 63 DALI terminals, for a higher load on the DALI terminals no
more than 8 DALI terminals should be used. Especially when using DALI sensors,
the desired reaction time is an important criterion.
IB IL RS UNI, IB IL MBUS, IB IL RS 232-ECO, IB IL RS 485-ECO
These terminals are serial interfaces which can have 30 (MBus) or more slave
devices. The limiting factor is here the required poll rate or reaction time. The hard
limit is 16 serial terminals, but then no other terminals could be added. We
recommend to use 8 terminals at the most.
With Modbus RTU, the max. number of about 4-5 messages per second can be
achieved with one connected terminal IL IL RS UNI. When 8 such terminals are
connected, the poll rate drops to about 2 messages per second (for each terminal).