ifm
Supplementary device manual Interface CANopen in the AS-i controllerE
Terms, abbreviations
109
Polling
to poll = to count votes
The controller master fetches the data from every participant in the system
successively:
Master calls participant 1.
Participant 1 replies with its current data (actual values).
Master transfers more data (target values) to participant 1, if needed.
Participant 1 acknowledges reception of the data,
etc., the same procedure for each further participant.
Cyclical polling: AS-i master cyclically polls the data of all slaves in 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.
Ethernet
Fieldbus system for larger data volumes, it requires special cables, complex
connection technology. Available in different versions as Ethernet-DP or -PA.
The Ethernet-DP can be used as a supplier for AS-i over longer distances.
Corresponding
gateways are available.
Ethernet-DP
Ethernet-DP (
D
ecentralised
P
eriphery) to trigger sensors and actuators by a
central controller in production technology. In particular the numerous standard
diagnostic options are important. More applications are the connection of
"distributed intelligence", i.e. networking of several controllers among each
(similar to
Ethernet-FMS). Data rates up to 12 Mbits/s on twisted two-wire
cables and/or fibre optics are possible.
Ethernet-PA
Ethernet-PA (
P
rocess
A
utomation) is used for the control of measurement
devices by a process control system in process technology. This ETHERNET
variant is suitable for hazardous areas (zones 0 and 1). Here, 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 is 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.
RTS
RTS =
R
un
T
ime
S
ystem
Runtime systems are basic versions of applications. These minimum versions
are supplied with certain products to meet the prerequisites for the execution of
the actual product or to be able to look at or use results generated by this
product on other processors: making available all routines required to execute a
program in a programming language, e.g. interactions with the
operating
system, memory requirements, error routines, inputs and outputs.
