P80C54SBAA View Datasheet(PDF) - NXP Semiconductors.

Part Name

Description

Manufacturer

P80C54SBAA

80C51 8-bit microcontroller family 8K–64K/256–1K OTP/ROM/ROMless, low voltage (2.7V–5.5V), low power, high speed (33 MHz)

NXP Semiconductors. 

Philips Semiconductors

80C51 8-bit microcontroller family

8K–64K/256–1K OTP/ROM/ROMless, low voltage (2.7V–5.5V),

low power, high speed (33MHz)

Product specification

8XC54/58

8XC51FA/FB/FC/80C51FA

8XC51RA+/RB+/RC+/RD+/80C51RA+

When Timer 2 is in the baud rate generator mode, one should not try

to read or write TH2 and TL2. As a baud rate generator, Timer 2 is

incremented every state time (osc/2) or asynchronously from pin T2;

under these conditions, a read or write of TH2 or TL2 may not be

accurate. The RCAP2 registers may be read, but should not be

written to, because a write might overlap a reload and cause write

and/or reload errors. The timer should be turned off (clear TR2)

before accessing the Timer 2 or RCAP2 registers.

Table 5 shows commonly used baud rates and how they can be

obtained from Timer 2.

Summary Of Baud Rate Equations

Timer 2 is in baud rate generating mode. If Timer 2 is being clocked

through pin T2(P1.0) the baud rate is:

Baud

Rate

+

Timer

2

Overflow

16

Rate

If Timer 2 is being clocked internally , the baud rate is:

Baud Rate + [32

fOSC

[65536 * (RCAP2H, RCAP2L)]]

Where fOSC= Oscillator Frequency

To obtain the reload value for RCAP2H and RCAP2L, the above

equation can be rewritten as:

ǒ Ǔ RCAP2H, RCAP2L + 65536 * 32

fOSC

Baud Rate

Timer/Counter 2 Set-up

Except for the baud rate generator mode, the values given for

T2CON do not include the setting of the TR2 bit. Therefore, bit TR2

must be set, separately, to turn the timer on. See Table 6 for set-up

of Timer 2 as a timer. Also see Table 7 for set-up of Timer 2 as a

counter.

Table 6. Timer 2 as a Timer

MODE

16-bit Auto-Reload

16-bit Capture

Baud rate generator receive and transmit same baud rate

Receive only

Transmit only

INTERNAL CONTROL

(Note 1)

00H

01H

34H

24H

14H

T2CON

EXTERNAL CONTROL

(Note 2)

08H

09H

36H

26H

16H

Table 7. Timer 2 as a Counter

MODE

16-bit

Auto-Reload

INTERNAL CONTROL

(Note 1)

02H

03H

TMOD

EXTERNAL CONTROL

(Note 2)

0AH

0BH

NOTES:

1. Capture/reload occurs only on timer/counter overflow.

2. Capture/reload occurs on timer/counter overflow and a 1-to-0 transition on T2EX (P1.1) pin except when Timer 2 is used in the baud rate

generator mode.

2000 Aug 07

18

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