Types Of Program Memories - Mitsubishi FX-20P-E Operation Manual

FX-20P-E Handy programming panel
3.4

Types of program memories

Memory cassette Memory board
(for the FX /FX/ (for the FX
0N
FX /FX Series PLC)
2C 2N
F X - E E P R O M - 4 C
2 N C
F X - E E P R O M - 1 6 ( C )
2 N C
FX-RAM-8
FX-EEPROM-4
FX-EEPROM-8
FX-EEPROM-16
FX-EPROM-8
Write-protect switch
M e m o r y c a s s e t t e M e m o r y b o a r d
Memory cassette
• RAM (random access memory)
(for the FX /
2NC 1S
FX Series PLC)
1N
F X - E E P R O M - 8 L
1 N
8 L ® P L C
W R
O N
P R O T E C T
S W
• EEPROM (electrically erasable programmable read only
O F F
R D
8 L ¬ P L C
• EPROM (erasable programmable read only memory)
• The saved contents are kept saved against power failure.
• Even if the EEPROM and the EPROM are attached to the
M e m o r y c a s s e t t e
The RAM can be read and written at any time. Because the
saved contents are erased by power failure, the RAM should
be backed up by the battery. And the saved contents are
erased also when the RAM is removed from the PLC.
The RAM is used also as the internal memory of the HPP
and the PLC.
memory)
The EEPROM is read only memory (ROM), and can be
written at any time by applying a specified voltage.
The saved contents are kept saved against power failure.
The total number of allowable write occasions is restricted
by the life expectancy. The life expectancy is 10,000 times
for memory cassettes and memory boards, and 20,000
times for the EEPROM built in the PLC. The write-protect
switch is provided to prevent erroneous write.
The EPROM is read only memory. The saved contents are
erased by irradiation of ultraviolet rays.
After all saved contents are erased, new contents can be
batch-written by the ROM writer.
PLC, a dedicated battery or large capacitor is required to
back up the image memory.
Outline of Programming 3
3-4