T80C5112-RKSCV datasheet(31/97 Pages) ATMEL

31 / 97 page

Rev. B - November 10, 2000

Preliminary

T80C5112

11. Serial I/O Ports enhancements

The serial I/O ports in the T80C5112 are compatible with the serial I/O port in the 80C52.

They provide both synchronous and asynchronous communication modes. They operate as Universal Asynchronous

Receiver and Transmitter (UART) in three full-duplex modes (Modes 1, 2 and 3). Asynchronous transmission and

reception can occur simultaneously and at different baud rates

Serial I/O ports include the following enhancements:

· Framing error detection

· Automatic address recognition

11.1. Framing Error Detection

Framing bit error detection is provided for the three asynchronous modes (modes 1, 2 and 3). To enable the framing

bit error detection feature, set SMOD0 bit in PCON register (See Figure 10).

Figure 10. Framing Error Block Diagram

When this feature is enabled, the receiver checks each incoming data frame for a valid stop bit. An invalid stop

bit may result from noise on the serial lines or from simultaneous transmission by two CPUs. If a valid stop bit

is not found, the Framing Error bit (FE) in SCON register (See Table 18) bit is set.

Software may examine FE bit after each reception to check for data errors. Once set, only software or a reset can

clear FE bit. Subsequently received frames with valid stop bits cannot clear FE bit. When FE feature is enabled,

RI rises on stop bit instead of the last data bit (See Figure 11. and Figure 12.).

Figure 11. UART Timings in Mode 1

SM0 to UART mode control (SMOD0 = 0 for UART)

RB8

TB8

REN

SM2

SM1

IDL

GF0

GF1

POF

SMOD0

SMOD1

To UART framing error control

Set FE bit if stop bit is 0 (framing error) (SMOD0 = 1 for UART)

SCON for UART (98h) (SCON_1 for UART_1 (C0h))

PCON for UART (87h) (SMOD bits for UART_1

are located in BDRCON_1)

SM0/FE

Data byte

SMOD0=X

Stop

bit

Start

bit

RXD

SMOD0=1

T80C5112-RKSCV 数据表(PDF) 31 Page - ATMEL Corporation

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