P87LPC760 datasheet(35/56 Pages) PHILIPS

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Philips Semiconductors

Preliminary data

P87LPC760

Low power, low price, low pin count (14 pin)

microcontroller with 1 kbyte OTP

2002 Mar 07

BIT

SYMBOL

FUNCTION

SCON.7

Framing Error. This bit is set by the UART receiver when an invalid stop bit is detected. Must be

cleared by software. The SMOD0 bit in the PCON register must be 1 for this bit to be accessible.

See SM0 bit below.

SCON.7

SM0

With SM1, defines the serial port mode. The SMOD0 bit in the PCON register must be 0 for this bit

to be accessible. See FE bit above.

SCON. 6

SM1

With SM0, defines the serial port mode (see table below).

SM0, SM1

UART Mode

Baud Rate

0 0

0: shift register

CPU clock/6

0 1

1: 8-bit UART

Variable (see text)

1 0

2: 9-bit UART

CPU clock/32 or CPU clock/16

1 1

3: 9-bit UART

Variable (see text)

SCON.5

SM2

Enables the multiprocessor communication feature in Modes 2 and 3. In Mode 2 or 3, if SM2 is set

to 1, then Rl will not be activated if the received 9th data bit (RB8) is 0. In Mode 1, if SM2=1 then RI

will not be activated if a valid stop bit was not received. In Mode 0, SM2 should be 0.

SCON.4

REN

Enables serial reception. Set by software to enable reception. Clear by software to disable reception.

SCON.3

TB8

The 9th data bit that will be transmitted in Modes 2 and 3. Set or clear by software as desired.

SCON.2

RB8

In Modes 2 and 3, is the 9th data bit that was received. In Mode 1, it SM2=0, RB8 is the stop bit that

was received. In Mode 0, RB8 is not used.

SCON.1

Transmit interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or at the beginning

of the stop bit in the other modes, in any serial transmission. Must be cleared by software.

SCON.0

Receive interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or halfway through

the stop bit time in the other modes, in any serial reception (except see SM2). Must be cleared by

software.

SU01550

RB8

TB8

REN

SM2

SM1

SM0/FE

SCON

Reset Value: 00h

Bit Addressable

Address: 98h

Figure 31. Serial Port Control Register (SCON)

Baud Rates

The baud rate in Mode 0 is fixed: Mode 0 Baud Rate = CPU clock/6.

The baud rate in Mode 2 depends on the value of bit SMOD1 in

Special Function Register PCON. If SMOD1 = 0 (which is the value

on reset), the baud rate is 1/32 of the CPU clock frequency. If

SMOD1 = 1, the baud rate is 1/16 of the CPU clock frequency.

Mode 2 Baud Rate

+ 1 ) SMOD1

x CPU clock frequency

Using Timer 1 to Generate Baud Rates

When Timer 1 is used as the baud rate generator, the baud rates in

Modes 1 and 3 are determined by the Timer 1 overflow rate and the

value of SMOD1. The Timer 1 interrupt should be disabled in this

application. The Timer itself can be configured for either “timer” or

“counter” operation, and in any of its 3 running modes. In the most

typical applications, it is configured for “timer” operation, in the

auto-reload mode (high nibble of TMOD = 0010b). In that case the

baud rate is given by the formula:

Mode 1, 3 Baud Rate

CPU clock frequency

192 (or96ifSMOD1

+ 1)

256

* (TH1)

Tables 6 and 7 list various commonly used baud rates and how they

can be obtained using Timer 1 as the baud rate generator.

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