AT89C51AC3-RDTIM datasheet(70/141 Pages) ATMEL

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AT89C51AC3

4383A–8051–10/04

Interrupt

Each Timer handles one interrupt source that is the timer overflow flag TF0 or TF1. This

flag is set every time an overflow occurs. Flags are cleared when vectoring to the Timer

interrupt routine. Interrupts are enabled by setting ETx bit in IEN0 register. This assumes

interrupts are globally enabled by setting EA bit in IEN0 register.

Figure 39. Timer Interrupt System

Registers

Table 30. TCON Register

TCON (S:88h)

Timer/Counter Control Register

Reset Value = 0000 0000b

TF0

TCON.5

ET0

IEN0.1

Timer 0

Interrupt Request

TF1

TCON.7

ET1

IEN0.3

Timer 1

Interrupt Request

7654

3210

TF1

TR1

TF0

TR0

IE1

IT1

IE0

IT0

Bit

Number

Bit

Mnemonic

Description

7TF1

Timer 1 Overflow Flag

Cleared by hardware when processor vectors to interrupt routine.

Set by hardware on Timer/Counter overflow, when Timer 1 register overflows.

6TR1

Timer 1 Run Control Bit

Clear to turn off Timer/Counter 1.

Set to turn on Timer/Counter 1.

5TF0

Timer 0 Overflow Flag

Cleared by hardware when processor vectors to interrupt routine.

Set by hardware on Timer/Counter overflow, when Timer 0 register overflows.

4TR0

Timer 0 Run Control Bit

Clear to turn off Timer/Counter 0.

Set to turn on Timer/Counter 0.

3IE1

Interrupt 1 Edge Flag

Cleared by hardware when interrupt is processed if edge-triggered (see IT1).

Set by hardware when external interrupt is detected on INT1# pin.

2IT1

Interrupt 1 Type Control Bit

Clear to select low level active (level triggered) for external interrupt 1 (INT1#).

Set to select falling edge active (edge triggered) for external interrupt 1.

1IE0

Interrupt 0 Edge Flag

Cleared by hardware when interrupt is processed if edge-triggered (see IT0).

Set by hardware when external interrupt is detected on INT0# pin.

0IT0

Interrupt 0 Type Control Bit

Clear to select low level active (level triggered) for external interrupt 0 (INT0#).

Set to select falling edge active (edge triggered) for external interrupt 0.

AT89C51AC3-RDTIM Datasheet(PDF) 70 Page - ATMEL Corporation

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