Specifications
72
3706C–MICRO–2/11
AT89LP3240/6440
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 b y 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 dat
a 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/Cou
nter 2 Compare/Capture Flags
T2CCF Address = 0D5H Reset Value = XXXX 0000B
Not Bit Addressable
– – – – CCFD CCFC CCFB CCFA
Bit76543210
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
T2CCCT2CCL T2CCH
0
1
2
3
4
5
6
7
“0”
Timer 0 Overflow
Timer 1 Overflow
Comparator A
Comparator B
00H 00H
CTCx
CCFx
CIENx
CxM
2-0