
Functional Controller Module (FCM)
MC68HC08LK60 MC68HC908LK60 Advance Information Data Sheet, Rev. 1.1
100
Freescale Semiconductor
8.8.1 Timebase Control Register
This timebase control register (TBCR) is a read/write register containing control bits for the timebase
outputs which feed other circuits.
RTCE — Real-time clock enable bit
When set to 1, the real-time clock counters are enabled. This bit is cleared by reset.
NOTE
Enabling this bit will affect the clock that increments the seconds counter. It
is recommended that this write be performed at the start of the reset
sequence, to limit any timing discrepancies resulting from the timebase
clocks.
TBCLR — Timebase clear bit
When set to 1, the timebase counter chain is cleared. This bit will automatically clear after the timebase
clear function has occurred. This bit will always read a 0 and is cleared by reset.
NOTE
Clearing the timebase by setting TBCLR will affect all clocks derived from
the timebase, including the real-time clock inputs and the LCD.
CHRC — Chronograph clear bit
This bit clears all bits in the chronograph data register and holds it at that state until this bit is cleared
by software.
0 = Allows chronograph data register to begin counting
1 = Clears chronograph data register and holds value at $00
CRS1 and CRS0 — COP rate select bit
The value of these two bits determines the watchdog timer (WDT) timeout rate. These bits can be
written only on the first write to this register after reset. If these bits are never written to, the WDT reset
rate will be set at one second.
NOTE
Although these bits default to 0, the user should write to these bits to
prevent subsequent writes from changing the timeout rate.
A bit set/clear for any bit in this register is executed as a read-modify-write
of this register. If used as the first write to this register, further writes to
CRS[1:0] would not be valid, and the default value would be set.
Address:
$0035
Bit 7
654321
Bit 0
Read:
RTCE
0
CHRC
CRS1
CRS0
R
TB2X
TB0
Write:
TBCLR
Reset:
00000000
R= Reserved
Figure 8-4. Timebase Control Register (TBCR)