ifm
Device manual AS-i M4 Gateway Profibus DPV1 (AC1375, AC1376)
2012-02-23
Glossary of Terms
509
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
extended to 10 ms.
D
Data image (AS-i)
see
process image; Sum of all digital and
analogue input and output data.
As regards the time, the data image represents
the current condition of each individual slave
and NOT a consistent image of the entire AS-i
network at an exact point in time.
DeviceNet
Fieldbus system for larger data volumes based
on
CAN technology, requires special cables,
complex connection technology. Can be used
e.g. as a supplier for AS-i over longer
distances. Corresponding
gateways are
available.
DHCP
DHCP =
D
ynamic
H
ost
C
onfiguration
P
rotocol
= protocol for the dynamic configuration by
the
host
DHCP is a protocol that provides dynamic
configuration of IP addresses and associated
information. The protocol supports use of
IP addresses which are only available in
limited number by a centralised management
of the address assignment.
The participant logs on to a server with this
service when it is switched on in a network for
the first time. The server assigns a local free
IP address to the participant.
Diagnosis
During the diagnosis, the "state of health" of
the device is checked. It is to be found out if
and what faults are given in the device.
Depending on the device, the inputs and
outputs can also be monitored for their correct
function.
- wire break,
- short circuit,
- value outside range.
For diagnosis, configuration and log data can
be used, created during the "normal" operation
of the device.
The correct start of the system components is
monitored during the initialisation and start
phase. Errors are recorded in the log file.
For further diagnosis, self-tests can also be
carried out.
DRAM
DRAM =
D
ynamic
R
andom
A
ccess
M
emory
Technology for an electronic memory module
with random access (Random Access
Memory, RAM). The memory element is a
capacitor which is either charged or
discharged. It becomes accessible via a
switching transistor and is either read or
overwritten with new contents. The memory
contents are volatile: the stored information is
lost in case of lacking operating voltage or too
late restart.
E
EMV
EMC =
E
lectro
M
agnetic
C
ompatibility
According to the EC directive (2004/108/EEC)
concerning electromagnetic compatibility (in
short EMC directive) requirements are made
for electrical and electronic apparatus,
equipment, systems or components to operate
satisfactorily in the existing electromagnetic
environment. The devices must not interfere
with their environment and must not be
adversely influenced by external
electromagnetic interference.
Ethernet
Ethernet is a widely used, manufacturer-
independent technology which enables data
transmission in the network at a speed of 10 or
100 million bits per second (Mbps). Ethernet
belongs to the family of so-called "optimum
data transmission" on a non exclusive
transmission medium. The concept was
developed in 1972 and specified as
IEEE 802.3 in 1985.
