ST92F124 datasheet(178/426 Pages) STMICROELECTRONICS

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EXTENDED FUNCTION TIMER (EFT)

EXTENDED FUNCTION TIMER (Cont’d)

10.3.4 Interrupt Management

The interrupts of the Extended Function Timer are

mapped on one of the eight External Interrupt

Channels of the microcontroller (refer to the “Inter-

rupts” chapter).

The three interrupt sources are mapped on the

same interrupt channel. To use them, the EFTIS

bit must be set)

Each External Interrupt Channel has:

– A trigger control bit in the EITR register (R242 -

Page 0),

– A pending bit in the EIPR register (R243 - Page

0),

– A mask bit in the EIMR register (R244 - Page 0).

Program the interrupt priority level using the EI-

PLR register (R245 - Page 0). For a description of

these registers refer to the “Interrupts” and “DMA”

chapters.

Using the external interrupt channel for all EFT

interrupts

To use the interrupt features, perform the following

sequence:

– Set the priority level of the interrupt channel used

(EIPLR register)

– Select the interrupt trigger edge as rising edge

(set the corresponding bit in the EITR register)

– Set the EFTIS bit of the CR3 register to select

the peripheral interrupt sources

– Set the OCIE (or OC1IE/OC2IE bits) and/or ICIE

(or IC1IE/IC2IE bits and/or TOIE bit(s) in the CR1

– In the EIPR register, reset the pending bit of the

interrupt channel used by the peripheral inter-

rupts to avoid any spurious interrupt requests be-

ing performed when the mask bit is set

– Set the mask bits of the interrupt channels used

to enable the MCU to acknowledge the interrupt

requests of the peripheral.

– Clear all EFT interrupt flags by reading the Sta-

tus, Input Capture Low, Output Compare Low

and Counter Low Registers.

Caution:

1. It is mandatory to clear all EFT interrupt flags

simultaneously at least once before exiting an

EFT timer interrupt routine (the SR register

must = 00h at some point during the interrupt

routine), otherwise no interrupts can be issued

on that channel anymore.

Refer to the following assembly code for an

interrupt sequence example.

2. Since a loop statement is needed inside the IT

routine, the user must avoid situations where

an interrupt event period is narrower than the

duration of the interrupt treatment. Otherwise

nested interrupt mode must be used to serve

higher priority requests.

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