AT89LP6440 datasheet(71/194 Pages) ATMEL

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3706A–MICRO–9/09

AT89LP6440 - Preliminary

13.2

Input Capture Mode

The Compare/Capture Array provides a variety of capture modes suitable for time-stamping

events or performing measurements of pulse width, frequency, slope, etc. CCA channels are

configured for capture mode by clearing the CCMx bit in the associated CCCx register to 0.

Each time a capture event occurs, the contents of Timer 2 (TH2 and TL2) are transferred to the

16-bit data register of the corresponding channel, and the channel’s interrupt flag CCFx is set in

T2CCF. Optionally, the capture event may also clear Timer 2 to 0000H by setting the CTCx bit in

CCCx. The capture event is defined by the CxM

2-0 bits in CCCx and may be either externally or

internally generated. A diagram of a CCA channel in capture mode is shown in Figure 13-2.

Figure 13-2. CCA Capture Mode Diagram

Each CCA channel has an associated external capture input pin: CCA (P2.0), CCB (P2.1), CCC

(P2.2) and CCD (P2.3). External capture events are always edge-triggered and can be selected

Table 13-4.

T2CCF – Timer/Counter 2 Compare/Capture Flags

T2CCF Address = 0D5H

Reset Value = XXXX 0000B

Not Bit Addressable

–

CCFD

CCFC

CCFB

CCFA

Bit

654

321

Symbol

Function

CCFD

Channel D Compare/Capture Interrupt Flag. Set by a compare/capture event on channel D. Must be cleared by software.

CCFD will generate an interrupt when CIEND = 1 and ECC = 1.

CCFC

Channel C Compare/Capture Interrupt Flag. Set by a compare/capture event on channel C. Must be cleared by

software. CCFC will generate an interrupt when CIENC = 1 and ECC = 1.

CCFB

Channel B Compare/Capture Interrupt Flag. Set by a compare/capture event on channel B. Must be cleared by software.

CCFB will generate an interrupt when CIENB = 1 and ECC = 1.

CCFA

Channel A Compare/Capture Interrupt Flag. Set by a compare/capture event on channel A. Must be cleared by software.

CCFA will generate an interrupt when CIENA = 1 and ECC = 1.

TL2

TH2

CCxL

CCxH

CCCx

Interrupt

(P2.x) CCx

T2CCC

T2CCL

T2CCH

“0”

Timer 0 Overflow

Timer 1 Overflow

Comparator A

Comparator B

00H

CTCx

CCFx

CIENx

CxM2-0

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