■ Operation of Clock Supply Function
The MB91350A uses a timebase counter to secure the oscillation stabilization wait time after INIT or stop
mode. On the other hand, the MB91350A uses the watch timer to secure the subclock oscillation
stabilization wait time while the main clock is selected as the clock source. This is because the watch timer
operates with the subclock regardless of clock source selection.
Follow the procedure below to perform subclock oscillation stabilization wait operation while the
MB91350A is operating on the main clock:
1. Set the interval time for the watch timer to "1" second (when F
to "0" (by writing "11" to the WS1 and WS0 bits and "0" to the WCL bit).
If it is necessary to perform processing after the end of the oscillation stabilization wait with an
interrupt, initialize the interrupt flag (by writing "0" to the WIF bit and "1" to WIE bit).
2. Start subclock oscillation (by writing "1" to Bit 11 [PLL2EN bit] of CLKR).
3. In the program, wait until the WIF flag is set to "1".
4. Make sure that the WIF flag has been set to "1", then perform the processing to be done after the end of
the oscillation stabilization wait. If interrupts are enabled, an interrupt is generated when the WIF bit is
set to "1". Then, perform the processing to be done after the end of the oscillation stabilization wait by
an interrupt routine. If it is necessary to switch the clock source from the main clock to subclock, switch
the clock source after making sure that the WIF bit has been set to "1" as described above. (If the clock
source is switched to the subclock before subclock oscillation is stabilized, unstable clock is supplied to
the entire device and subsequent operation is unpredictable.)
= 32.768 kHz), and clear the counter