P90CE201 datasheet(49/77 Pages) PHILIPS

49 / 77 page

August 1993

Philips Semiconductors

Product speciﬁcation

16-bit microcontroller

P90CE201

9.3.2

UART CONTROL REGISTER (SCON)

The Serial Port Control Register and Status Register (SCON) contains not only the mode selection bits, but also the 9th

data bit for transmit and receive (TB8 and RB8), and the serial port interrupt bits (TI and RI). SCON has a default value

of 00H.

Table 42 Description of SCON bits.

Table 43 Selection of the serial port modes.

SYMBOL

BIT

FUNCTION

SM0

SM1

SCON.7

SCON.6

These two bits are used to select the serial port mode. See Table 43.

SM2

SCON.5

Enables the multiprocessor communication feature in Modes 2 and 3. In Modes 2

and 3, if SM2 = 1, then RI will not be activated if the received 9th data bit (RB8) is

a logic 0. In Mode 1, if SM2 = 1, then RI will not be activated unless a valid stop bit

was received. In Mode 0, SM2 should be a logic 0.

REN

SCON.4

Enables serial reception and is set by software to enable reception, and cleared

by software to disable reception.

TB8

SCON.3

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

software as required.

RB8

SCON.2

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

then 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 time 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 transmission

(however see SM2). Must be cleared by software.

SM0

SM1

MODE

DESCRIPTION

BAUD RATE

Shift register

BPCLK/4

8-bit UART

variable

9-bit UART

3/32 BPCLK

9-bit UART

variable

Fig.32 UART Control Register (SCON).

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

SM0

SM1

SM2

REN

TB8

RB8

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