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Supplementary device manual DeviceNet interface in the AS-i ControllerE (AC1318, AC1324), Target from 15
2012-02-29
Glossary of Terms
232
FE – functional earth
F
unctional
e
arth is a reference potential which
is not connected to protective earth or only
connected when special measures are taken.
The functional earth serves as equalisation of
potential for an ungrounded installation (e.g.
SELV).
Fieldbus
A
bus for industrial applications:
mechanically extremely robust and excellent
data protection.
Firmware
System software, basic program in the device,
virtually the operating system.
The firmware establishes the connection
between the hardware of the device and the
user software. This software is provided by the
manufacturer of the controller as a part of the
system and cannot be changed by the user.
Flash memory
Flash ROM (or flash EPROM or flash memory)
combines the advantages of semiconductor
memory and hard disks. Just like every other
semiconductor memory the flash memory does
not require moving parts. And the data is
maintained after switch-off, similar to a hard
disk.
The flash ROM evolved from the EEPROM
(
E
lectrical
E
rasable and
P
rogrammable
R
ead-
O
nly
M
emory). The storage function of data in
the flash ROM is identical to the EEPROM.
Similar to a hard disk, the data are however
written and deleted blockwise in data blocks up
to 64, 128, 256, 1024, ... bytes at the same
time.
Advantages of flash memories
The stored data are maintained even if
there is no supply voltage.
Due to the absence of moving parts, flash
is noiseless and insensitive to shocks and
magnetic fields.
In comparison to hard disks, flash
memories have a very short access time.
Read and write speed are virtually
constant across the entire memory area.
The memory size that can be obtained has
no upper limit, due to the simple and
space-saving arrangement of the storage
cells.
Disadvantages of flash memories
A storage cell can tolerate a limited
number of write and delete processes:
- Multi-level cells: typ. 10 000 cycles
- Single level cells: typ. 100 000 cycles
Given that a write process writes memory
blocks of between 16 and 128 Kbytes at
the same time, memory cells which require
no change are used as well.
FMEA
FMEA =
F
ailure
M
ode and
E
ffects
A
nalysis
Method of reliability engineering, to find
potential weak points. Within the framework of
quality or security management, the FMEA is
used preventively to prevent faults and
increase the technical reliability.
FRAM
FRAM, or also FeRAM, means
Fe
rroelectric
R
andom
A
ccess
M
emory. The storage
operation and erasing operation is carried out
by a polarisation change in a ferroelectric
layer.
Advantages of FRAM as compared to
conventional read-only memories:
non-volatile,
compatible with common EEPROMs, but:
access time approx. 100 ns,
nearly unlimited access cycles possible.
G
Gateway
Gateway = access, coupler
Gateways enable connection of completely
different systems. Gateways are used when
two incompatible network types are to be
connected by converting the protocol of one
system to the protocol of the other system.
Example: connection between AS-i and higher-
level fieldbus systems such as
Ethernet DP,
DeviceNet, Interbus-S or other interfaces,
e.g. RS-485. The device includes an AS-i
master which is directly coupled to the
host
interface (e.g.
Ethernet DP slave).
