MC68HC705MC4MP datasheet(142/180 Pages) FREESCALE

No. de pieza	MC68HC705MC4MP

Descripción Electrónicos	General Release Specification

PDF	180 Pages

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Fabricante Electrónico	FREESCALE [Freescale Semiconductor, Inc]

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Core Timer

MC68HC705MC4 — Rev. 2.0

Core Timer

RTIE — Real-Time Interrupt Enable

When this bit is set, a CPU interrupt request is generated when the

RTIF bit is set. Reset clears this bit.

RT1:RT0 — Real-Time Interrupt Rate Select

These two bits select 1-of-4 taps from the real-time interrupt circuit.

Table 12-1 shows the available interrupt rates with several f

OP values.

Reset sets these RT0 and RT1, selecting the lowest periodic rate and

therefore the maximum time in which to alter these bits if necessary.

Care should be taken when altering RT0 and RT1 if the time-out

period is imminent or 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 RTI taps.

Table 12-1. RTI Rates

RT1:RT0

RTI Rates at Bus Frequency of:

16.384 kHz

3.0 MHz

Divide Ratio

1 sec

5.5 ms

214

2 sec

10.9 ms

215

3 sec

21.8 ms

216

8 sec

43.75 ms

217

Freescale Semiconductor, Inc.

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MC68HC705MC4MP Datasheet(PDF) 142 Page - Freescale Semiconductor, Inc