MC68HC908AZ60A — Rev 2.0 Technical Data

MOTOROLA Computer Operating Properly (COP) 223

Technical Data — MC68HC908AZ60A

Section 15. Computer Operating Properly (COP)

15.1 Contents

15.2 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223

15.3 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .224

15.4 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225

15.4.1 CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225

15.4.2 STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225

15.4.3 COPCTL Write. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226

15.4.4 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226

15.4.5 Internal Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226

15.4.6 Reset Vector Fetch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226

15.4.7 COPD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226

15.4.8 COPL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226

15.5 COP Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227

15.6 Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227

15.7 Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227

15.8 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227

15.8.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227

15.8.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .228

15.9 COP Module During Break Interrupts . . . . . . . . . . . . . . . . .228

15.2 Introduction

The COP module contains a free-running counter that generates a reset

if allowed to overflow. The COP module helps software recover from

runaway code. Prevent a COP reset by periodically clearing the COP

counter.

Computer Operating Properly (COP)

Technical Data MC68HC908AZ60A — Rev 2.0

224 Computer Operating Properly (COP) MOTOROLA

15.3 Functional Description

The COP counter is a free-running 6-bit counter preceded by a 12-bit

prescaler. If not cleared by software, the COP counter overflows and

generates an asynchronous reset after 2

–2

or 2

–2

CGMXCLK

cycles, depending on the state of the COP long timeout bit, COPL, in the

CONFIG-1. When COPL = 0, a 4.9152-MHz crystal gives a COP timeout

period of 53.3 ms. Writing any value to location $FFFF before an

overflow occurs prevents a COP reset by clearing the COP counter and

stages 4–12 of the SIM counter.

NOTE: Service the COP immediately after reset and before entering or after

exiting stop mode to guarantee the maximum time before the first COP

counter overflow.

A COP reset pulls the RST pin low for 32 CGMXCLK cycles and sets the

COP bit in the reset status register (RSR).

In monitor mode, the COP is disabled if the RST pin or the IRQ pin is held

at V

. During the break state, V

on the RST pin disables the COP.

NOTE: Place COP clearing instructions in the main program and not in an

interrupt subroutine. Such an interrupt subroutine could keep the COP

from generating a reset even while the main program is not working

properly.

Computer Operating Properly (COP)

I/O Signals

MC68HC908AZ60A — Rev 2.0 Technical Data

MOTOROLA Computer Operating Properly (COP) 225

15.4 I/O Signals

The following paragraphs describe the signals shown in Figure 15-1.

15.4.1 CGMXCLK

CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency

is equal to the crystal frequency.

15.4.2 STOP Instruction

The STOP instruction clears the COP prescaler.

Figure 15-1. COP Block Diagram

COPCTL WRITE

CGMXCLK

RESET VECTOR FETCH

RESET

RESET STATUS

INTERNAL RESET SOURCES

STOP INSTRUCTION

CLEAR STAGES 4–12

CLEAR ALL STAGES

6-BIT COP COUNTER

COPD FROM CONFIG-1

RESET

COPCTL WRITE

CLEAR COP

COUNTER

COPL FROM CONFIG-1

12-BIT COP PRESCALER

Part #	8A/S6
Description	Incandescent S Light Lamp
Category	LAMP
Availability	In Stock
Qty	2

8A/S6

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