IFM Ecomat 300 AC1307, Основное руководство устройства

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17BTerms and abbreviations
18-5
Polling
The controller master fetches the data from every participant
in the system successively:
1. Master calls participant 1
2. Participant 1 replies with its current data (current values)
3. Master transfers more data (preset values) to partici-
pant 1 if necessary
4. Participant 1 acknowledges receipt of the data
etc., the same procedure for all other participants.
Cyclical polling: AS-i master cyclically polls the data of all
→
slaves on the bus (see above). The data is updated in the
→
master after max. 5 ms. If A/B slaves are used, the
→
cycle
time can be 10 ms.
Profibus Fieldbus system for larger data volumes, requires special
cables, complex connection technology. Is available in differ-
ent variants as
→
Profibus FMS, DP or PA. Profibus DP can
be used over longer distances, e.g. as fieldbus for AS-i. Cor-
responding
→
gateways are available.
Profibus FMS Profibus FMS (
F
ieldbus
M
essage
S
pecification) to network
controllers – no longer standardised from 2007
Profibus DP Profibus DP (
D
ecentralised
P
eriphery) to trigger sensors
and actuators by a central controller in production technol-
ogy. In particular the numerous standard diagnostic options
are important. More applications are the connection of "dis-
tributed intelligence", i.e. networking of several controllers
among each other (similar to
→ Profibus FMS). Data rates up
to 12 Mbits/s on twisted two-wire cables and/or fibre optics
are possible.
Profibus PA Profibus PA (
P
rocess
A
utomation) is used to control field
devices by means of a process control system in process
technology. This PROFIBUS variant is suitable for hazardous
areas (zones 0 and 1). Only a small current flows on the bus
cables in an intrinsically safe circuit so that even in case of a
problem no sparks are produced. The disadvantage of this
variant is the slower data transmission rate.
Remanent Remanent data are protected against data loss in case of
power failure.
The operating system for example automatically copies the
remanent data to a flash memory as soon as the voltage
supply falls below a critical value. If the voltage supply is
available again the operating system loads the remanent
data back to the RAM memory.
The data in the RAM memory of a controller, however, is
volatile and normally lost in case of power failure.