mc68hc705k1 Freescale Semiconductor, Inc, mc68hc705k1 Datasheet - Page 78

• Manufacturer Part Number: mc68hc705k1
• Description: Hcmos Microcontroller Unit
• Manufacturer: Freescale Semiconductor, Inc

Multifunction Timer
Technical Data
NOTE:
RTIE — Real-Time Interrupt Enable Bit
TOFR — Timer Overflow Flag Reset
RTIFR — Real-Time Interrupt Flag Reset
RT1 and RT0 — Real-Time Interrupt Select Bits 1 and 0
Changing RT1 and RT0 when a COP timeout is imminent or uncertain
may cause an RTI request to be missed or an additional RTI request to
be generated. Clear the COP timer just before changing RT1 and RT0.
1. At 2-MHz bus, 4-MHz XTAL, 0.5 s per cycle
RT1:RT0
This read/write bit enables real-time interrupts. Reset clears RTIE.
Writing a logic 1 to this write-only bit clears the TOF bit. TOFR always
reads as a logic 0. Reset does not affect TOFR.
Writing a logic 1 to this write-only bit clears the RTIF bit. RTIFR
always reads as a logic 0. Reset does not affect RTIFR.
These read/write bits select one of four real-time interrupt rates, as
shown in
watchdog, changing the real-time interrupt rate also changes the
counting rate of the COP watchdog. Reset sets RT1 and RT0,
selecting the longest COP timeout period and RTI period.
Freescale Semiconductor, Inc.
0 0
0 1
1 0
1 1
For More Information On This Product,
1 = Real-time interrupts enabled
0 = Real-time interrupts disabled
Table 8-1. Real-Time Interrupt Rate Selection
Table
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2
2
2
2
17
14
15
16
of Cycles
Number
Multifunction Timer
to RTI
= 131,072
= 16,384
= 32,768
= 65,536
8-1. Because the selected RTI output drives the COP
Period
16.4 ms
32.8 ms
65.5 ms
8.2 ms
RTI
(1)
2
to COP Reset
2
2
2
20
17
18
19
of Cycles
Number
= 1,048,576
= 131,072
= 262,144
= 524,288
MC68HC705K1 — Rev. 2.0
COP Timeout
Period
131.1 ms
262.1 ms
524.3 ms
65.5 ms
(1)