Motorola MCF5282, MCF5281 user manual Periodic/Interval Timer, Qadc Clock Subsystem Functions

Models: MCF5282 MCF5281

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Digital Control Subsystem

System Clock

Divide by 2

Input Sample Time

 

from CCW

2

Queue 1 and Queue 2 Timer

8

Mode Rate Selection

QPR[6:0]

Prescaler

ATD Converter

State Machine

Binary Counter

27

28

29

210

211

212

213

214

215

216

217

Periodic Timer/Interval Timer

Select

SAR Control

SAR 10

Periodic/Interval Trigger

2 Event for Q1 and Q2

Figure 27-42. QADC Clock Subsystem Functions

CAUTION

A change in the prescaler value while a conversion is in progress is likely to corrupt the result. Therefore, any prescaler write operation should be done only when both queues are in the disabled modes.

To accommodate the wide range of the system clock frequency, QCLK is generated by a programmable prescaler which divides the system clock. To allow the A/D conversion time to be maximized across the spectrum of system clock frequencies, the QADC prescaler permits the QCLK frequency to be software selectable. The frequency of QCLK is set with the QPR field in QACR0.

27.8.9 Periodic/Interval Timer

The QADC periodic/interval timer can be used to generate trigger events at a programmable interval, initiating execution of queue 1 and/or queue 2. The periodic/interval timer stays reset under these conditions:

Both queue 1 and queue 2 are programmed to any mode which does not use the periodic/interval timer.

System reset is asserted.

Stop mode is enabled.

Debug mode is enabled.

27-58

MCF5282 User’s Manual

MOTOROLA

Page 642
Image 642
Motorola MCF5282, MCF5281 user manual Periodic/Interval Timer, Qadc Clock Subsystem Functions