235
MMI
HMI
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Modbus
The Modbus protocol is a communication
protocol based on a
master/slave
architecture and was generated by Modicon in
1979 for communication with its PLCs. In the
industry, Modbus has become a de facto
standard.
Modbus/TCP is based on
Ethernet TCP/IP.
Modbus/TCP ports the protocol defined for the
serial interface to TCP. The
IP address
clearly identifies each device in a network.
Therefore the slave address was used to
identify one of several logical units (unit IDs) in
a physical device. To do so, the extended
IP addressing is used.
Example: 192.168.83.28.1 means unit ID 1 on
IP address 192.168.83.28.
*) Modicon passed from AEG to the group
Schneider in 1994.
MRAM
MRAM means
M
agnetoresistive
R
andom
A
ccess
M
emory. The information is stored by
means of magnetic storage elements. The
property of certain materials is used to change
their electrical resistance when exposed to
magnetic fields.
Advantages of MRAM as compared to
conventional RAM memories:
non volatile (like FRAM), but:
access time only approx. 35 ns,
unlimited number of access cycles
possible.
MSB
M
ost
S
ignificant
B
it/Byte
O
Operating system
Basic program in the device, establishes the
connection between the hardware of the
device and the user software.
OSC
OSC =
O
nline
S
upport
C
enter
Help system in the device
OSSD
OSSD =
O
utput
S
ignal
S
witching
D
evice
= output signal of a switching device. Here:
output signal of an AS-i safety monitor.
P
Password
In the menu [System Setup], menu item
[Password] the handling can be restricted or
enabled. When delivered, the device is in the
user mode. By entering an invalid password
(e.g. 1000) all menu items which can change
settings are blocked.
PCCD
PCCD =
P
rojected
C
TT
C
onfiguration
D
ata
Configuration data for the 7.4 and 7.5 slaves
stored in the device:
- Manufacturer ID,
- Vendor ID,
- Device ID,
- Device Group ID.
PCD
PCD =
P
rojected
C
onfiguration
D
ata
Configuration data stored in the device:
LPS and AS-i profile (IO, ID, ID1, ID2)
PDM
PDM =
P
rocess and
D
ialogue
M
odule
Device for communication of the operator with
the machine / plant.
PELV
PELV =
P
rotective
E
xtra
L
ow
V
oltage
Functional extra low voltage with safe
separation, grounded variant of SELV.
Extra low voltage with safe separation
(grounded variant of SELV). The specification
as PELV system to IEC 364-4-41 covers a
measure to protect against direct and indirect
contact with dangerous voltages by a "safe