MC68HC705JD FREESCALE [Freescale Semiconductor, Inc], MC68HC705JD Datasheet - Page 45

• Manufacturer Part Number: MC68HC705JD
• Description: member of the low-cost
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Rev. 2
RT1:RT0
TOF — Timer Overflow Flag
RTIF — Real-Time Interrupt Flag
TOIE — Timer Overflow Interrupt Enable
RTIE — Real-Time Interrupt Enable
Bits 3 and 2 — Not used. Always read as zeros.
RT1, RT0 — Real-Time 1 and 0
0 0
0 1
1 0
1 1
This clearable, read-only bit becomes set when the first eight stages of the counter
roll over from $FF to $00. TOF generates a timer overflow interrupt request if
TOFE is also set. Clear TOF by writing a zero to it. Writing a one to TOF has no
effect.
This clearable, read-only bit becomes set when the selected RTI output becomes
active. RTIF generates a real-time interrupt request if RTIE is also set. Clear RTIF
by writing a zero to it. Writing a one to RTIF has no effect.
This read/write bit enables timer overflow interrupts.
This read/write bit enables real-time interrupts
These read/write bits select one of four real-time interrupt rates. See
The real-time interrupt rate should be selected by reset initialization software. A
reset sets both RT1 and RT0, selecting the lowest real-time interrupt rate.
Changing the real-time interrupt rate near the end of the RTI period or during a
cycle in which the counter is switching can produce unpredictable results.
Because the selected RTI output drives the COP timer, changing the real-time
interrupt rate also changes the counting rate of the COP timer.
1 = Timer overflow interrupts enabled
0 = Timer overflow interrupts disabled
1 = Real-time interrupts enabled
0 = Real-time interrupts disabled
RTI Rate
f
f
f
f
op
op
op
op
2
2
2
2
14
15
16
17
Table 7-1. Real-Time Interrupt Rate Selection
Freescale Semiconductor, Inc.
For More Information On This Product,
(f
RTI Period
op
16.4 ms
32.8 ms
65.5 ms
8.2 ms
= 2 MHz)
Go to: www.freescale.com
TIMER
COP Timeout Period
(-0/+1 RTI Period)
7
7
7
7
RTI Period
RTI Period
RTI Period
RTI Period
Minimum COP Timeout
Period ( f
114.7 ms
229.4 ms
458.8 ms
57.3 ms
op
= 2 MHz)
Table
7-1.
7-3
10
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
9