參數(shù)資料
型號: MC68HC05X4CDWR2
廠商: FREESCALE SEMICONDUCTOR INC
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 2.2 MHz, MICROCONTROLLER, PDSO28
封裝: PLASTIC, SOIC-28
文件頁數(shù): 10/168頁
文件大?。?/td> 656K
代理商: MC68HC05X4CDWR2
Core Timer
Core timer registers
MC68HC05X4 Rev 1.0
MOTOROLA
Core Timer
107
5-ctimer
This bit is set when the output of the chosen stage becomes active;
an interrupt request will be generated if RTIE is set. When set, the bit
may be cleared by writing a ‘0’ to it.
CTOE — Core timer overflow interrupt enable
1 = A core timer overflow interrupt will be generated if CTOF is set
and the I-bit in the CCR is clear.
0 = No core timer overflow interrupt will be generated regardless of
the state of the CTOF flag and the I-bit.
RTIE — Real time interrupt enable
0 = A real time interrupt will be generated if RTIF is set and the I-bit
in the CCR is clear.
0 = No real time interrupt will be generated regardless of the state
of the RTIF flag and the I-bit.
RT1, RT0 — Real time interrupt rate select
These two bits select one of four taps from the real time interrupt
circuitry. Reset sets both RT0 and RT1 to one, selecting the lowest
periodic rate and therefore the maximum time in which to alter them if
necessary. The COP reset times are also determined by these two
bits. Care should be taken when altering RT0 and RT1 if a timeout is
imminent, or if the timeout period is uncertain. If the selected tap is
modified during a cycle in which the counter is switching, an RTIF
could be missed or an additional one could be generated. To avoid
problems, the COP should be cleared before changing the RTI taps.
See Table 1 for some example RTI periods.
Table 1. Example RTI periods
Bus frequency
fOP = 500 kHz
Bus frequency
fOP = 1 MHz
Bus frequency
fOP = 2 MHz
RT1 RT0
Division
ratio
RTI
period
Minimum
COP
period
RTI
period
Minimum
COP
period
RTI
period
Minimum
COP
period
00
214
31.3ms
218.8ms
15.6ms
109.4ms
7.8ms
54.7ms
01
215
62.5ms
437.5ms
31.3ms
218.8ms
15.6ms
109.4ms
10
216
125ms
875.0ms
62.5ms
437.5ms
31.3ms
218.8ms
11
217
250ms
1.75s
125.1ms
875.0ms
62.5ms
437.5ms
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