PixArt Imaging Inc.

PAC107

All rights strictly reserved any portion in this paper shall not be reproduced, copied or transformed to any other forms without permission.

41

PixArt Imaging Inc.

E-mail:

fae_service@pixart.com.tw

V1.4, Aug, 2005

In most applications, timer 1 is configured as a timer in auto-reload mode (high nibble of

TMOD = 0010B). The resulting baud rate is defined by the following expression:

Timer 1 can generate very low baud rates with the following setup:

•

Enable the timer 1 interrupt by setting the ET1 bit in the IE register.

•

Configure timer 1 to run as a 16-bit timer (high nibble of TMOD = 0001B).

•

Use the timer 1 interrupt to initiate a 16-bit software reload.

Timer 2 Generated Baud Rates (Modes 1 and 3)

Timer 2 may be selected as the baud rate generator for the transmitter and/or receiver. The

timer 2 baud rate generator mode is similar to the auto-reload mode. A rollover in the TH2

register reloads registers TH2 and TL2 with the 16-bit value on registers RCAP2H and

RCAP2L, which are preset by software.

The timer 2 baud rate is expressed by the following formula:

Selecting Timer 2 as the Baud Rate Generator

Program the RCLCK and TCLCK bits in the T2CON. A rollover in the TH2 register does

not set the TF2 bit in the T2CON register. And a high-to-low transition at T2EX pin sets the

EXF2 bit in the T2CON register but does not cause a reload from (RCAP2H, RCAP2L) to

(TH2, TL2). TT2EX pin cab be used as an additional external interrupt by setting the

EXEN2 bit in T2CON.

NOTE

: Please turn off the timer before accessing registers TH2, TL2, RCAP2H, and

RCAP2L(clear the TR2 bit in the T2CON register).

You may configure timer 2 as a timer or a counter. In most applications, it is configured for

timer operation (i.e., the C/T2 bit is clear in the T2CON register).

Selecting the Baud Rate Generator(s)

2

SMOD

Fosc

32 X 12 X [256 - (Th1)]

Sreial I/O Mode 1 and 3 Baud Rate

Timer 2 Onerflow Rate

16

Sreial I/O Mode 1 and 3 Baud Rate