AT89LV52 View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

AT89LV52

8-Bit Microcontroller with 8K Bytes Flash

Atmel Corporation 

Not

16-bit value in RCAP2H and RCAP2L. The values in

RCAP2H and RCAP2L are preset by software. If EXEN2 =

1, a 16-bit reload can be triggered either by an overflow or

by a 1-to-0 transition at external input T2EX. This transition

also sets the EXF2 bit. Both the TF2 and EXF2 bits can

generate an interrupt if enabled.

Setting the DCEN bit enables Timer 2 to count up or down,

as shown in Figure 3. In this mode, the T2EX pin controls

the direction of the count. A logic 1 at T2EX makes Timer 2

count up. The timer will overflow at 0FFFFH and set the

TF2 bit. This overflow also causes the 16-bit value in

Figure 2. Timer 2 Auto Reload Mode (DCEN = 0)

RCAP2H and RCAP2L to be reloaded into the timer regis-

ters, TH2 and TL2, respectively.

A logic 0 at T2EX makes Timer 2 count down. The timer

underflows when TH2 and TL2 equal the values stored in

RCAP2H and RCAP2L. The underflow sets the TF2 bit and

causes 0FFFFH to be reloaded into the timer registers.

The EXF2 bit toggles whenever Timer 2 overflows or

underflows and can be used as a 17th bit of resolution. In

this operating mode, EXF2 does not flag an interrupt.

OSC

÷12

T2 PIN

C/T2 = 0

C/T2 = 1

CONTROL

TR2

RELOAD

TH2

TL2

RCAP2H RCAP2L

OVERFLOW

TIMER 2

INTERRUPT

T2EX PIN

TRANSITION

DETECTOR

TF2

EXF2

CONTROL

EXEN2

Table 4. T2MOD—Timer 2 Mode Control Register

T2MOD Address = 0C9H

Reset Value = XXXX XX00B

Not Bit Addressable

—

—

—

—

—

—

T2OE

DCEN

Bit

7

6

5

4

3

2

1

0

Symbol

—

T2OE

DCEN

Function

Not implemented, reserved for future use.

Timer 2 Output Enable bit.

When set, this bit allows Timer 2 to be configured as an up/down counter.

4-89

Share Link: