P87LPC779FDH datasheet(47/74 Pages) PHILIPS

47 / 74 page

Philips Semiconductors

P87LPC779

CMOS single-chip 8-bit microcontroller

Product data

Rev. 02 — 03 May 2004

47 of 74

9397 750 13213

8.15.6

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.

(4)

Table 37:

SCON - Serial port control register (address 98H) bit description

Bit

Symbol

Description

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.

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.

SM1

With SM0, deﬁnes the serial port mode (see Table 38 below).

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.

REN

Enables serial reception. Set by software to enable reception.

Clear by software to disable reception.

TB8

The 9th data bit that will be transmitted in Modes 2 and 3. Set or

clear by software as desired.

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.

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.

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.

Table 38:

SM0, SM1 serial port mode

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)

Mode 2 baud rate

SMOD1

------------------------------

CPU clock frequency

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