参数资料
型号: MC68HC05P9AMDW
厂商: FREESCALE SEMICONDUCTOR INC
元件分类: 微控制器/微处理器
英文描述: 8-BIT, MROM, 2.1 MHz, MICROCONTROLLER, PDSO28
封装: SOIC-28
文件页数: 158/158页
文件大小: 3885K
代理商: MC68HC05P9AMDW
Timer
I/O Registers
Timer
Alternate Timer
Registers
The read-only alternate timer registers (ATRH and ATRL) contain the
current high and low bytes of the 16-bit counter. Reading ATRH before
reading ATRL causes ATRL to be latched until ATRL is read. Reading
does not affect the timer overflow flag (TOF). Writing to the alternate
timer registers has no effect.
Reading ATRH returns the current value of the high byte of the counter
and causes the low byte to be latched into a buffer.
Figure 56. Alternate Timer Register Reads
NOTE:
To prevent interrupts between readings of ATRH and ATRL, set the
interrupt mask (I bit) in the condition code register before reading ATRH,
and clear the mask after reading ATRL.
$001A
Bit 7
654321
Bit 0
Read:
Bit 15
14
13
12
11
10
9
Bit 8
Write:
Reset:
Reset initializes ATRH to $FF
$001B
Bit 7
654321
Bit 0
Read:
Bit 7
654321
Bit 0
Write:
Reset:
Reset initializes ATRL to $FC
= Unimplemented
Figure 55. Alternate Timer Registers (ATRH and ATRL)
ATRH ($001A)
ATRL ($001B)
BUFFER
INTERNAL
DATA BUS
READ ATRH
LATCH
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For More Information On This Product,
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