CP 523
Technical Description
2.5
Integral Hardware Clock
The CP incorporates a hardware clock which is backed up by the battery of the PLC power supply
module.
Using the clock data
You can use the clock data in two ways:
•
The current clock data can be inserted in a message text. You can insert spaceholders for date
and time of day for this purpose when configuring the message texts ( 6.4).
•
The current clock data can be read out by the CPU and used in the user program ( 6.6 or
7.4.2).
Battery backup of the clock data
The clock is backed up by the battery of the PLC power supply module.
The clock starts with the default values Sunday 1.1.90 12:00:00 on power-up.
The power supply module battery should only be replaced in the POWER ON state, as otherwise
the clock data is lost and the clock must be reset.
Default setting
The clock is factory-set to Sunday 1.1.90 12:00:00
Setting the time and date
You can set the clock:
•
In the user program (see Section 6.7.2 for details)
•
With the "FORCE VAR" programmer function (refer to the example ”Writing to word 0 of the
transfer buffer with the CPU 944 using ”FORCE VAR” in Section 5.2).
Output format of the clock data in the message text
You can configure how the current clock data is to be output to the printer ( 6.3.3).
The default is:
•
For the date: <Day> . <Month> . <Year>
•
For the time: <Hours> : <Minutes> : <Seconds>
Accuracy of the integral real-time clock
The accuracy of the clock is t
g
=±2s/day.
Temperature dependency of the clock
The temperature dependency T
D
of the clock is T
D
=3.5 (T
A
-15)
2
ms/day at an ambient tempera-
ture of T
A
.
Correction value
You can configure a correction value to enhance the accuracy of the clock (Print mode 6.3.6,
Communications mode 7.3.1 and 7.3.2). The correction value is given in s/month. A month is
defined as 30 days.
Example:
Determining the correction value
You have observed that the clock loses 12 s in 4 days. This would be 90 s in 30 days. The correction
value is then 90 s/month.
EWA 4NEB 811 6044-02a
2-11
