12.5 Operation Of Watch Prescaler; Figure 12.5-1 Interval Timer Function Settings - Fujitsu F2MC-8L Series Hardware Manual

12.5 Operation of Watch Prescaler

The watch prescaler provides the interval timer and clock supply functions.
Interval Timer Operation (Watch Prescaler)
Figure 12.5-1 shows the settings required to operate the watch prescaler as the interval timer.
WPCR
The 15-bit counter of the watch prescaler keeps on incrementing with the subclock as the count
clock as long as the subclock oscillates.
When the counter is cleared (WCLR = "0"), it restarts incrementing the count from "0000
When the count reaches "7FFF
When the counter encounters the rising edge of the frequency-divided output selected for the
interval timer, the watch interrupt request flag bit (WIF) is set to "1" if not in main-sotp mode.
That is, the watch prescaler generates watch interrupt request at the selected time intervals,
with the time at which the counter is cleared,used as the reference point of time.
Clock Supply Operation
The watch prescaler can also serve as the timer for producing the subclock oscillation
stabilization delay time. The subclock oscillation stabilization delay time (2
subclock oscillation) is the time from when the watch prescaler starts incrementing the count
after being cleared to when the MSB is set low.
The watch prescaler supplies clock signals to the watchdog timer and buzzer output. Clearing
the watch prescaler counter has an effect on operation of the buzzer output. The watchdog
timer counter is cleared at the same time if the watch prescaler output has been selected as its
count clock (WDTC: CS = "1").
Watch Prescaler Operation
Figure 12.5-2 shows each value that the counter has when the device enters sleep mode or
stop mode, or when a counter clear request is issued, during operation of the watch prescaler
as the interval timer in subclock mode.
When the device enters watch mode, the watch prescaler operate in the same way as when the
device enters sub-sleep mode.

Figure 12.5-1 Interval Timer Function Settings

Bit 7 Bit 6 Bit 5 Bit 4
WIF WIE —
0 1
", it returns to "0000
H
12.5 Operation of Watch Prescaler
Bit 3 Bit 2 Bit 1
— — WS1 WS0
" and the counter continues counting.
H
Bit 0
: Used bit
WCLR
1 : Set "1".
0
0 : Set "0".
15
/F , where F
CL
".
H
is
CL
269