Real-time clock

At a Glance

Each processor (Premium or Atrium) has a savable real-time clock which manages:

The date and time are managed even when the processor is switched off, on condition that:

the Premium processor is mounted on the rack with its power supply module in place and is equipped with a back-up battery,
the Atrium processor is equipped with a back-up battery.

Current date and time

the processor keeps the current date and time up to date in the system words %SW49 to %SW53. This data is coded in BCD.

System words	Most significant byte	Least significant byte
%SW49	00	Days of the week from 1 to 7 (1 for Monday and 7 for Sunday)
%SW50	Seconds (0 to 59)	00
%SW51	Hours (0 to 23)	Minutes (0 to 59)
%SW52	Month (1 to 12)	Days of the month (1 to 31)
%SW53	Century (0 to 99)	Year (0 to 99)
%SW70		Week (1 to 52)

NOTE: %SW49 is read-only.

Accessing the date and time

The date and time can be accessed:

via the processor debug screen,
via the program:
- read: system words %SW49 to %SW53, if the system bit %S50 = 0,
- immediate update: write system words %SW50 to %SW53, if the system bit %S50 = 1,
- incremental update: the system word %SW59 is used to change the date and time, field by field, from the current value, if the system bit %S59 = 1, or is used to carry out a global increment/decrement.

Bit value table:

bit0 = 1, increments the date and time globally (1)	bit8 = 1, decrements the date and time globally (1)
bit1 =1, increments the seconds	bit9 =1, decrements the seconds
bit2 =1, increments the minutes	bit10 =1, decrements the minutes
bit3 =1, increments the hours	bit11 =1, decrements the hours
bit4 =1, increments the days	bit12 =1, decrements the days
bit5 =1, increments the months	bit13 =1, decrements the months
bit6 =1, increments the years	bit14 =1, decrements the years
bit7 =1, increments the centuries	bit15 =1, decrements the centuries

(1) all fields are updated.

NOTE: The processor does not automatically manage the change between winter and summer time.

The date and time of when the application last stopped

The date and time of when the application last stopped are stored in BCD in the system words %SW54 to %SW58.

System words	Most significant byte	Least significant byte
%SW54	Seconds (0 to 59)	00
%SW55	Hours (0 to 23)	Minutes (0 to 59)
%SW56	Month (1 to 12)	Days of the month (1 to 31)
%SW57	Century (0 to 99)	Year (0 to 99)
%SW58	Day of the week (from 1 to 7)	Reason for the last application stop

to access the date and time of the last application stop:

read the system words %SW54 to %SW58,
to find the reason for the last application stop:

read the least significant byte of the system word %SW58 (value saved in BCD).

Table of %SW58 system words:

%SW58 = 1	application switched to STOP mode,
%SW58 = 2	application stopped due to a software error,
%SW58 = 4	power outage or power supply RESET button has been pressed
%SW58 = 5	stop due to hardware fault
%SW58 = 6	application stopped due to HALT instruction