A8351601L-40 查看數據表（PDF） - AMIC Technology

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A8351601L-40

Bar Code Reader

AMIC Technology 

A8351601 Series

Timer 2

Timer 2 is a 16-bit Timer/Counter present only in the

A8351601. This is a powerful addition to the other two just

discussed. Five extra special function registers are added

to accommodate Timer 2 which are: the timer registers,

TL2 and TH2, the timer control register, T2CON, and the

capture registers, RCAP2L and RCAP2H. Like Timers 0

and 1, it can operate either as a timer or as an event

counter, depending on the value of bit C/T2 in the Special

Function Register T2CON. Timer 2 has three operating

modes: capture, auto-reload, and baud rate generator,

which are selected by RCLK, TCLK, CP/RL2 and TR2.

In the Capture Mode, the EXEN2 bit in T2CON selects two

options. If EXEN2=0, then Timer 2 is a 16-bit timer or

counter whose overflow sets bit TF2, the Timer 2 overflow

bit, which can be used to generate an interrupt. If

EXEN2=1, then Timer 2 performs the same way, but a 1-

to-0 transition at external input T2EX also causes the

current value in the Timer 2 registers, TL2 and TH2, to be

captured into the RCAP2L and RCAP2H registers,

respectively. In addition, the transition at T2EX sets the

EXF2 bit in T2CON, and EXF2, like TF2, can generate an

interrupt.

The Capture Mode is illustrated in Figure 6.

In the auto-reload mode, the EXEN2 bit in T2CON also

selects two options. If EXEN2 = 0, then when Timer 2 rolls

over it sets TF2 and also reloads the Timer 2 registers with

the 16-bit value in the RCAP2L and RCAP2H registers,

which are preset by software. If EXEN2 = 1, then Timer 2

performs the same way, but a 1-to-0 transition at external

input T2EX also triggers the 16-bit reload and sets EXF2.

The auto-reload mode is illustrated in Figure 7.

The baud rate generator mode is selected by RCLK = 1

and/or TCLK = 1. This mode is described in conjunction

with the serial port (Figure 8).

OSC

DIVIDE 12

C/T2=0

T2 PIN

C/T2=1

TRANSITION

DETECTOR

TL2

TH2

(8 BITS) (8 BITS)

CONTROL

TR2

CAPTURE

RCAP2L RCAP2H

T2EX PIN

CONTROL

EXEN2

TF2

EXF2

Figure 6. Timer 2 in Capature Mode

TIMER 2

INTERRUPT

(July, 2002, Version 1.0)

16

AMIC Technology, Inc.

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