FX Series Programmable Controllers Assigning System Devices 9
9-7
9.4 Real Time Clock Function
When one of the real time clock (RTC) memor
cassettes is used with either and FX or an
FX0N, the real time clock function of that PLC is then automaticall
enabled.
The time data of the RTC cassette is batter
backed. This means when the PLC is turned OFF
the time data and settin
s are not lost or corrupted. The duration or stora
e life of the time data
is dependent upon the condition of the batter
. The operation of the RTC clock circuits
consumes ne
li
ible currents compared with the RAM memor
(applicable to FX onl
).
The real time clock cassettes have a worst case accurac
of ± 45 seconds per month at an
ambient temperature of 25
°
C. The calendar function of the RTC cassettes caters for leap
ears durin
the period 1980 throu
h 2079.
FX PLC’s Pre Version 2.0
• These PLC’s do not support the RTC function.
Available RTC Cassettes:
Function Registers And Control Flags:
• Please see pa
e 6-3 for a list of the available clock devices.
• Please see section 5.14 (pa
e 5-138) for RTC supportin
functions with FX2N.
General Use Of Memory Cassettes
• FX and FX
2C
Main Processin
units can use an
of the available memor
cassette t
pes.
FX
0N
units can onl
use EEPROM or EPROM t
pe Memor
Cassettes and then onl
a
maximum of 2k steps can be accessed.
• It is necessar
to install a FX
0N
-40BL batter
to maintain the RTC time with FX
0N
controllers.
• The FX
2N
has a real time clock built in to the MPU. Althou
h it is possible to use the RTC
cassettes for memor
, it is not necessar
to use them to obtain the RTC function.
RTC Cassette Remark
FX-RTC Real time clock function onl
FX-RAM-8C
Real time clock function + 8K RAM
(Note: the FX
0N
cannot use this cassette,
because RAM pro
ram stora
e is not
uaranteed)
FX-EEPROM-4C
Real time clock function + 4K EEPROM
(Note the FX
0N
can onl
use 2K of the EEPROM)
