Z51F0410 Datasheet, PDF (80/184 Pages) Zilog, Inc. – Z8051 Series 8-Bit Microcontrollers

Z51F0410
Product Specification
4.4 WT
4.4.1 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.
4.4.2 Block Diagram
fSUB
(32.768kHz)
P
r
÷64
e
fx
s
c
÷128
a
l
e
÷256
r
MUX
fWCK
14Bit
fWCK / 2¹⁴
Timer Counter
Binary Counter
(7bit auto reload counter)
fWCK / 2¹⁴ x (7bit WTR Value +1)
7
fWCK/2¹⁴
fWCK/2¹³
fWCK/2¹²
MUX
WTIFR
WTIF
Clear
WTMR WTEN -
- WTIFR WTIN1 WTIN0 WTCK1 WTCK0
2
INT_ACK
WTR
WTR Write
WTCR
WTR Read
WTCL WTR6 WTR5 WTR4 WTR2 WTR2 WTR1 WTR0
- WTCR6 WTCR5 WTCR4 WTCR2 WTCR2 WTCR1 WTCR0
Figure 4.5 Watch Timer Block Diagram
4.4.3 Register Map
Name
WTMR
WTR
WTCR
Address
9DH
9EH
9EH
Table 4.4 WT Register Map
Dir
R/W
W
R
Default
00H
7FH
00H
Description
Watch Timer Mode Register
Watch Timer Register
Watch Timer Counter Register
4.4.4 Watch Timer Register description
The watch timer register (WT) consists of Watch Timer Mode Register (WTMR), Watch Timer
Counter Register (WTCR) and Watch Timer Register (WTR). As WTMR is 6-bit writable/readable
PS029502-0212
PRELIMINARY
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