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AN913

APPLICATION NOTE

PWM GENERATION WITH THE ST62

16-BIT AUTO-RELOAD TIMER

by 8-bit Micro Application Team

INTRODUCTION

This note presents how to use the ST62 16-bit Auto-Reload Timer (ARTimer) for generating a

DTMF signal (Dual-Tone Multiple Frequency) with the PWM. In the example shown, the PWM

output pin generates a DTMF to dial a telephone number.

1 16-BIT AUTO-RELOAD TIMER DESCRIPTION

This timer is a 16-bit downcounter timer with prescaler (see Figure 1.). It includes auto-reload

PWM, capture and compare capability with two input (CP1, CP2) and two output pins (OVF,

PWM). It is controlled by the following registers:

– Status control registers (8-bit) SCR1, SCR2, SCR3, SCR4

– CP Capture register pair (16-bits total): CPH and CPL

– MASK register pair (16-bits total): MASKH and MASKL

– TC 16-bit downcounter register

– CMP Compare register pair (16-bits total): CMPH and CMPL

– RLCP Reload/Capture register pair (16-bits total): RLCPH and RLCPL

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