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Z51F6412
Product Specification
PS030302-0212
P R E L I M I N A R Y
67
11.4 WT
11.4.1 Overview
The watch timer has the function for RTC (Real Time Clock) operation. It is generally used for RTC
design. The internal structure of the watch timer consists of the clock source select circuit, timer
counter circuit, output select circuit and watch timer mode register. To operate the watch timer,
determine the input clock source, output interval and set WTEN to ‘1’ in watch timer mode register
(WTMR). It is able to execute simultaneously or individually. To stop or reset WT, clear the WTEN bit
in WTMR register. Even if CPU is STOP mode, sub clock is able to be alive so WT can continue the
operation. The watch timer counter circuits may be composed of 21-bit counter which is low 14-bit
with binary counter and high 7-bit with auto reload counter in order to raise resolution. In WTR, it can
control WT clear and set Interval value at write time, and it can read 7-bit WT counter value at read
time.
11.4.2 Block Diagram
11.4.3 Register Map
Table 11-5 Register Map
Name
Address
Dir
Default
Description
WTMR
9DH
R/W
00H
Watch Timer Mode Register
WTR 9EH
W
7FH
Watch
Timer
Register
WTCR
9EH
R
00H
Watch Timer Counter Register
÷
128
fx
P
r
e
s
c
a
l
e
r
MUX
WTR
÷
64
14Bit
Binary Counter
WTR Write
÷
256
f
SUB
(32.768kHz)
f
WCK
/ 2
14
Timer Counter
(7bit auto reload counter)
MUX
WTIFR
WTEN
-
-
WTIFR WTIN1 WTIN0 WTCK1 WTCK0
WTCL WTR6 WTR5 WTR4 WTR2 WTR2 WTR1 WTR0
-
WTCR6 WTCR5 WTCR4 WTCR2 WTCR2 WTCR1 WTCR0
WTCR
WTR Read
WTMR
7
f
WCK
f
WCK
/2
14
f
WCK
/2
13
f
WCK
/2
11
2
f
WCK
/ 2
14
x (7bit
WTR Value +1)
WTIF
Clear
INT_ACK
Figure 11-5 Watch Timer Block Diagram