TABLE OF CONTENTS (Continued)

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viii

MC68HC901 USER’S MANUAL

MOTOROLA

Section 3

Bus Operation

3.1

Data Transfer Operations ......................................................................... 3-1

3.1.1

Read Cycle .......................................................................................... 3-1

3.1.2

Write Cycle .......................................................................................... 3-2

3.2

Interrupt Acknowledge Operation ............................................................. 3-2

3.3

Reset Operation ....................................................................................... 3-3

Section 4

Interrupt Structure

4.1

Interrupt Processing ................................................................................. 4-1

4.1.1

Interrupt Channel Prioritization ............................................................ 4-1

4.1.2

Interrupt Vector Number ...................................................................... 4-1

4.1.3

Vector Register (VR) ........................................................................... 4-2

4.2

Daisy-Chaining MFPs ............................................................................... 4-3

4.3

Interrupt Control Registers ....................................................................... 4-4

4.3.1

Interrupt Enable Registers (IERA, IERB) ............................................ 4-4

4.3.2

Interrupt Pending Registers (IPRA, IPRB) .......................................... 4-6

4.3.3

Interrupt Mask Registers (IMRA, IMRB) .............................................. 4-8

4.3.4

Interrupt In-Service Registers (ISRA, ISRB) ..................................... 4-10

4.4

Nesting MFP Interrupts ........................................................................... 4-11

4.4.1

Selecting the End-Of-Interrupt Mode ................................................. 4-11

4.4.2

Automatic End-Of-Interrupt Mode ..................................................... 4-12

4.4.3

Software End-Of-Interrupt Mode ....................................................... 4-12

Section 5

General Purpose Input/Output Port

5.1

GPIP Control Registers ............................................................................ 5-1

5.1.1

General Purpose I/O Data Register (GPDR) ....................................... 5-1

5.1.2

Active Edge Register (AER) ................................................................ 5-1

5.1.3

Data Direction Register (DDR) ............................................................ 5-2

Section 6

Timers

6.1

Operation Modes ...................................................................................... 6-1

6.1.1

Delay Mode Operation ........................................................................ 6-1

6.1.2

Pulse Width Measurement Operation ................................................. 6-2

6.1.3

Event Count Mode Operation .............................................................. 6-3

6.2

Timer Registers ........................................................................................ 6-4