MPC89X53AF datasheet(19/38 Pages) MEGAWIN

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Baud-Rate Generator Mode (BRG)

Timer2 can be configured to generate various baud-rates. Bit TCLK and/or RCLK in T2CON

allow the serial port transmit and receive baud rates to be derived from either Timer1 or

Timer2. When TCLK=0, Timer1 is used as the serial port transmit baud rate generator. When

TCLK=1, Timer2 is used as the serial port transmit baud rate generator. RCLK has the same

effect for the serial port baud rate. With these two bits, the serial port can have different

receive and transmit baud rates – one generated from Timer1 and the other from Timer2.

In BRG mode, Timers is operated very like auto-reload up-only mode except that the T2EX pin

cannot control reload.

An overflow on Timer2 will load RCAP2H, RCAP2L contents onto

Timer2, but TF2 will not be set. A 1-to-0 transition on P2EX pin can set EXF2 to request

interrupt service if EXEN2=1.

The baud rate in UART Mode1 and Mode3 are determined by Timer2’s overflow rate given

below:

Timer2 overflow rate

Baud Rate

(counting T2EX)

Oscillator Frequency

[32 x [65536 – (RCAP2H, RCAP2L) ] ]

Baud Rate =

(as a timer)

TL2[7:0]

TH2[7:0]

RCAP2L[7:0]

RCAP2H[7:0]

“1”

“0”

“1”

“0”

“0” “1”

Timer1 overflow

RX Clock

TX Clock

SMOD

RCLK

TCLK

Timer2 interrupt

T2EX pin

EXEN2

EXF2

TR2

OSC/12

T2 pin

C//T2

MEGAWIN

MPC89x53A Data Sheet

MPC89x53AF Datasheet(PDF) 19 Page - Megawin Technology Co., Ltd

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