
REAL TIMER (WATCH TIMER)
S3FB42F
13-2
WATCH TIMER CIRCUIT DIAGRAM
Frequency
Ddividing
Circuit
Clock
Selector
WTCON .1
WTCON .0
WTCON .2 .3
Enable/Disable
fw
(32768 Hz)
fw/27
fw/213
fw/214
fw/215 (1 HZ)
fw/23 (4 kHz)
fw/24 (2 kHz)
fw/25 (1 kHz)
fw/26 (0.5 kHz)
fx = Main system clock (f VCO or fxm)
fxx = Selected system clock (fx or fxt)
fxt = Sub system clock
fxm = Main osillator output
fvco = PLL Vco output
MUX
Selector
Circuit
WTCON .4 .5
Buzzer output
WT INT
Overflow
fxx/128
fxm
(P2.3)
Figure 13-1. Watch Timer Circuit Diagram