68
•
Board Support Package (BSP)
The Console of the Linux Fieldbus Coupler
WAGO-I/O-SYSTEM
750
Linux Fieldbus Coupler
4.3.4 Terminal Program (getty)
The console of the Linux fieldbus coupler is based on the terminal program
getty which processes the input and output via the serial interface.
The terminal program getty is started if the selector switch is in the upper
position during the boot process (condition upon delivery).
4.3.5 Setting the Hardware and System Clock
hwclock
can access the integrated hardware clock via the console drive (read
and write). The
date
console command sets the time of the system clock.
The difference between system clock and hardware clock is that the time will
still be stored in the hardware clock after a system reboot whereas the system
clock needs to be synchronized via the hardware clock after every system
reboot.
Standard time of the hardware clock is "Greenwich Main Time" (GMT or
UTC), the system time corresponds to the local time.
The system variable TZ determines the system time (local time).
The system variable is stored in the file
/etc/TZ
and describes the time
difference between a time zone and the "Greenwich Main Time".
The system variable TZ is defined as follows:
TZ = MEZ-1MESZ-2,M3.5.0,M10.5.0
•
MEZ:
Abbreviation for Central European Time
•
-1:
Information to calculate the standard time (time zones to the east of the
prime meridian are subtracted, time zones to the west of it are added)
•
MESZ:
Abbreviation for Central European Daylight Time
•
-2:
Information to calculate the daylight saving time (time zones to the east of
the prime meridian are subtracted, time zones to the west of it are added)
•
M:
3: Month, in which time is set to daylight saving time.
5: Week, in which time is set to daylight saving time.
0: Day (0 = Sunday), on which time is set to daylight saving time.
10: Month, in which time is set to standard time.
5: Week, in which time is set to standard time.
0: Day (0 = Sunday), on which time is set to standard time.
