AP160

Version 0.0

8

AMIC Technology, Inc.

Capture Mode

In the capture mode, two options are selected by bit EXEN2 in T2CON. If EXEN2=0, Timer 2 is a 16-bit timer or counter

which upon overflow sets bit TF2 in T2CON. This bit can then be used to generate an interrupt. If EXEN2=1, Timer 2

performs the same operation, but a 1-to-0 transition at external input T2EX also causes the current value in TH2 and TL2 to

be captured into RCAP2H and RCAP2L, respectively. In addition, the transition at T2EX causes bit EXF2 in T2CON to be

set. The EXF2 bit, like TF2, can generate an interrupt. The capture mode is illustrated in Figure 1.

TIMER 2

INTERRUPT

OSC

C/T2=0

T2 PIN

CONTROL

TH2

TF2

C/T2=1

TL2

RCAP2H

RCAP2L

EXF2

T2EX PIN

EXEN2

TR2

CAPTURE

CONTROL

TRANSITION

DETECTOR

12

÷

OVERFLOW

Figure 1. Timer in Capture Mode

Auto-Reload (UP or Down Counter)

Timer 2 can be programmed to count up or down when configured in its 16-bit auto-reload mode. This feature is invoked by

the DCEN (Down Counter Enable) bit located in the SFR T2MOD (see Table 3). Upon reset, the DCEN bit is set to 0 so that

Timer 2 will default to count up. When DCEN is set, Timer 2 can count up or down, depending on the value of the T2EX pin.

Figure 2 shows Timer 2 automatically counting up when DCEN=0.

TIMER 2

INTERRUPT

OSC

C/T2=0

T2 PIN

CONTROL

TH2

TF2

C/T2=1

TL2

RCAP2H

RCAP2L

T2EX PIN

EXEN2

TR2

RELOAD

CONTROL

TRANSITION

DETECTOR

12

÷

EXF2

OVERFLOW

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