AT89C5122DS-RDRUM datasheet(129/208 Pages) ATMEL

129 / 208 page

129

AT83R5122, AT8xC5122/23

4202F–SCR–07/2008

Baud Rate Selection (Mode 0)

In mode 0, baud rate can be either fixed or variable.

As shown in Figure 72, the selection is done using M0SRC bit in BDRCON register.

Figure 73 gives the baud rate calculation formulas for each baud rate source.

Figure 72.

Baud Rate Source Selection (Mode 0)

Figure 73.

Baud Rate Formulas (Mode 0)

Asynchronous Modes

(Modes 1, 2 and 3)

The Serial Port has one 8-bit and two 9-bit asynchronous modes of operation. Figure 74

shows the Serial Port block diagram in such asynchronous modes.

Figure 74.

Serial I/O Port Block Diagram (Modes 1, 2 and 3)

Mode 1

Mode 1 is a full-duplex, asynchronous mode. The data frame (see Figure 75) consists of

10 bits: one start, eight data bits and one stop bit. Serial data is transmitted on the TXD

pin and received on the RXD pin. When a data is received, the stop bit is read in the

RB8 bit in SCON register.

M0SRC

BDRCON.0

CK_

/ 6

To Serial Port

IBRG

CLOCK

Baud_Rate =

6(1-SPD)

⋅ 32 ⋅ (256 -BRL)

2SMOD1

⋅ F

CK_SI

BRL = 256 -

6(1-SPD)

⋅ 32 ⋅ Baud_Rate

2SMOD1

⋅ F

CK_SI

a. Fixed Formula

b. Variable Formula

Baud_Rate =

CK_SI

TB8

SCON.3

IBRG

CLOCK

RXD

TXD

SBUF Tx SR

Rx SR

SM1

SCON.6

SM0

SCON.7

Mode Decoder

M3 M2 M1 M0

SCON.0

SCON.1

Mode & Clock

Controller

SBUF Rx

RB8

SCON.2

SM2

SCON.4

CLOCK

CK_

AT89C5122DS-RDRUM 데이터시트(PDF) 129 Page - ATMEL Corporation

AT89C5122DS-RDRUM 데이터시트(HTML) 129 Page - ATMEL Corporation

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