參數(shù)資料
型號: MC68HC05PL4CSD
廠商: MOTOROLA INC
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 2.56 MHz, MICROCONTROLLER, PDSO28
封裝: SSOP-28
文件頁數(shù): 62/98頁
文件大小: 1019K
代理商: MC68HC05PL4CSD
April 30, 1998
GENERAL RELEASE SPECIFICATION
MC68HC05PL4
8-BIT TIMER
MOTOROLA
REV 2.0
10-3
T8EN - Timer8 Enable
This read/write bit enables the Timer8. Reset clears this bit.
1 =
Timer8 enabled
0 =
Timer8 disabled
PS2-PS0 - Prescaler select
These read/write bits is used to select the clock frequency to drive the 8-bit timer
counter. The counter will be driven by a internal bus clock (E-clock) through this
prescaler ratio. Upon reset and power on reset, the value of prescaler is set to a
default value of divided by 16.
10.3
TIMER8 COUNTER REGISTER (T8CNTR)
The T8CNTR is a read/write register which contains the current value of the 8-bit
timer counter. Reading this register enables the software to calculate the number
of internal and external clocks since the timer interrupt request ag (T8IF) was
set. Reading this address does not disturb the counter operation.
NOTE
This timer is used during the power-on sequence to time out the POR signal. The
timer is congured at power-on, with a prescaler division ratio of 16 and set to $FF
in Timer counter register. Also the clock source for the COP watchdog system is
derived from the output of this timer, hence a reset or preset of the prescaler and
timer counter register may affect the frequency of the watchdog timeout.
10.4
COMPUTER OPERATING PROPERLY (COP) WATCHDOG
Please refer to section on RESETS for details.
PS2
PS1
PS0
DIVIDE RATIO
000
1
001
2
010
4
011
8
1
0
16 (default after reset)
101
32
110
64
111
128
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
T8CNTR R
Timer 8 Counter Register
$000E
W
reset:
UUUUUUUU
Figure 10-3. Timer8 Counter Register
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