Outline Of Watch Timer - Fujitsu MB90390 Series Hardware Manual

CHAPTER 15 WATCH TIMER
15.1

Outline of Watch Timer

The Watch Timer consists of the Timer Control register, Sub-second register, Second/
Minute/Hour registers, 1/2 clock divider, 22-bit prescaler and Second/Minute/Hour
counters. The oscillation frequency of the MCU is assumed to be at 4MHz or 5MHz for
the aimed operation of the Watch Timer. The Watch Timer operates as the real-world
timer and provides the real-world time information.
■ Block Diagram of Watch Timer
Figure 15.1-1 shows a block diagram of the Watch Timer.
Oscillation
clock
1/2 Clock
Divider
UPDT ST
INTE0 INT0
238
Figure 15.1-1 Block Diagram of Watch Timer
EN
Second Counter
Minute Counter
CI
EN
LOAD CO
6bits
Second/Minute/Hour register
INTE1 INT1
22-bit prescaler
21bit Prescaler
CO
Sub-second
register
Hour Counter
CO
6bits 5bits
INTE2 INT2 INT3
OE
OE
WOT
CO
INT3
IRQ