ST92F120JR9T datasheet(136/320 Pages) STMICROELECTRONICS

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STANDARD TIMER (STIM)

10.2 STANDARD TIMER (STIM)

Important Note: This chapter is a generic descrip-

tion of the STIM peripheral. Depending on the ST9

device, some or all of the interface signals de-

scribed may not be connected to external pins. For

the list of STIM pins present on the particular ST9

device, refer to the pinout description in the first

section of the data sheet.

10.2.1 Introduction

The Standard Timer includes a programmable 16-

bit down counter and an associated 8-bit prescaler

with Single and Continuous counting modes capa-

bility. The Standard Timer uses an input pin (STIN)

and an output (STOUT) pin. These pins, when

available, may be independent pins or connected

as Alternate Functions of an I/O port bit.

STIN can be used in one of four programmable in-

put modes:

– event counter,

– gated external input mode,

– triggerable input mode,

– retriggerable input mode.

STOUT can be used to generate a Square Wave

or Pulse Width Modulated signal.

The Standard Timer is composed of a 16-bit down

counter with an 8-bit prescaler. The input clock to

the prescaler can be driven either by an internal

clock equal to INTCLK divided by 4, or by

CLOCK2 derived directly from the external oscilla-

tor, divided by device dependent prescaler value,

thus providing a stable time reference independ-

ent from the PLL programming or by an external

clock connected to the STIN pin.

The Standard Timer End Of Count condition is

able to generate an interrupt which is connected to

one of the external interrupt channels.

The End of Count condition is defined as the

Counter Underflow, whenever 00h is reached.

Figure 72. Standard Timer Block Diagram

STOUT1

EXTERN AL

INPUT

CLOCK CONTROL LOGIC

INEN INMD1 INMD2

STP

8-BIT PRESCALER

STH,STL

16-BIT

STAN DARD TIMER

CLOCK

OUTMD1 OUTMD2

OUTPU T CONTROL LOGIC

INTER RUPT

CONTROL LOGIC

END OF

COUNT

INTS

INTERRUPT REQUEST

CLOCK2/x

STIN1

INTERRUPT

DOWNCOUNTER

(See Note 2)

Note 2: Depending on device, the source of the INPUT & CLOCK CONTROL LOGIC block

may be permanently connected either to STI N or the RCCU signal CLOCK2/x. In devices without STI N and CLOCK2, the

INTCLK/4

MUX

Note 1: Pin not present on all ST9 devices

INEN bit must be held at 0.

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