Hardware manual

EUROCOM-17-5xx 3 Programmers Reference
Hardware Manual 77
3.13.2 Real-Time
Clock
The clock features BCD-coded year, month, day, hours, minutes, and
seconds as well as a software controlled calibration. For lifetime
calculations of the battery, please refer to the data sheet.
Access to the clock is as simple as conventional bytewide RAM access
because the RAM and the clock are combined in the same chip.
For further details, see the MK48T12/MK48T18 resp. DS1644 data
sheet.
The SRAM/RTC can only be accessed with byte instructions.
3.14 VIC Timer
The VIC contains a timer which can be programmed to output a periodic
wave form on LIRQ2. The frequencies available are 50Hz, 100Hz, and
1000Hz. The timer is enabled and controlled by writing slave select
control register0. The interrupt is enabled and controlled by writing local
interrupt control register2.
The clock tick timer is typically used as a time base for multi-tasking
operating systems, such as OS-9 or Lynx.
If other frequencies are needed, one of the six counters/timers that are
included in the two CIOs may be used. For more details about the timer,
refer to the VIC data sheet.
Table45: Address Assignment of the Real-Time Clock
MK48T12 Address Description
$FEC2.7FF8 RTC Control Register
$FEC2.7FF9 Seconds
$FEC2.7FFA Minutes
$FEC2.7FFB Hour
$FEC2.7FFC Day
$FEC2.7FFD Date
$FEC2.7FFE Month
$FEC2.7FFF Year
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