PixArt Imaging Inc.

PAC107

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32

PixArt Imaging Inc.

V1.4, Aug, 2005

RCLK and/or TCLK selects the baud rate generator mode.

T

selects Fosc/12 (timer operation) or

external pin T2 (counter operation) as the timer register input. Setting TF2 to be advanced

by the selected input.

Timer 2/ Capture Mode

Timer 2 function as a 16-bit timer or counter. An overflow condition sets bit TF2 to execute

ISR. Set the external enable bit EXEN2 allows the RCAP2Hand RCAP2L registers to

report the current value in timer registers TH2 and TL2 in response to a hi-to-lo transition

at external input T2EX. The transition at T2EX also sets bit EXF2 on T2CON. The EXF2

bit, like TF2, can generate an interrupt. TR2 must be enabled in this mode.

Timer 2/ Auto-reload Mode

The auto-reload mode configures timer 2 as a 16-bit timer or event counter with automatic

reload. The timer operates an as an up counter or as an up/down counter, as determined by

the down counter enable bit (DCEN). At device reset, DCEN is cleared, so in the

auto-reload mode, timer 2 defaults to operation as an up counter. TR2 must be enabled

when running

this mode.

Up Counter Operation

When DCEN = 0, timer 2 operates as an up counter. If EXEN = 0, timer 2 counts up to

FFFFH and sets the TF2 overflow flag. The overflow condition loads the 16-bit value in the

12

0

1

XTAL1

T2

TL2

(8 Bits)

Overflow

Interrupt

Request

TH2

(8 Bits)

TF2

RCAP2H

RCAP2L

T2EX

EXF2

EXEN2

TR2

Capture

C/ T2

Timer 2:Capture Mode