mc68hc05x4dw Freescale Semiconductor, Inc, mc68hc05x4dw Datasheet - Page 107

• Manufacturer Part Number: mc68hc05x4dw
• Description: Xc68hc705x4 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

5-ctimer
RT1 RT0
0
0
1
1
0
1
0
1
Division
ratio
2
2
2
2
14
15
16
17
CTOE — Core timer overflow interrupt enable
RTIE — Real time interrupt enable
RT1, RT0 — Real time interrupt rate select
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.
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
Freescale Semiconductor, Inc.
For More Information On This Product,
31.3ms
62.5ms
1 = A core timer overflow interrupt will be generated if CTOF is set
0 = No core timer overflow interrupt will be generated regardless of
0 = A real time interrupt will be generated if RTIF is set and the I-bit
0 = No real time interrupt will be generated regardless of the state
125ms
250ms
period
Bus frequency
RTI
f
Table 1
OP
Table 1. Example RTI periods
and the I-bit in the CCR is clear.
the state of the CTOF flag and the I-bit.
in the CCR is clear.
of the RTIF flag and the I-bit.
= 500 kHz
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Minimum
218.8ms
437.5ms
875.0ms
period
for some example RTI periods.
1.75s
COP
Core Timer
125.1ms
15.6ms
31.3ms
62.5ms
period
Bus frequency
RTI
f
OP
= 1 MHz
Minimum
109.4ms
218.8ms
437.5ms
875.0ms
period
COP
15.6ms
31.3ms
62.5ms
period
7.8ms
Bus frequency
RTI
f
OP
= 2 MHz
MC68HC05X4 Rev 1.0
Minimum
109.4ms
218.8ms
437.5ms
54.7ms
period
COP
Core timer registers
Core Timer