PIC18LF4331-ESLASHML datasheet(222/392 Pages) MICROCHIP

222 / 392 page

PIC18F2331/2431/4331/4431

DS39616D-page 222

 2010 Microchip Technology Inc.

EXAMPLE 20-1:

CALCULATING BAUD RATE ERROR

TABLE 20-2:

REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Reset Values

on Page:

TXSTA

CSRC

TX9

TXEN

SYNC

SENDB

BRGH

TRMT

TX9D

RCSTA

SPEN

RX9

SREN

CREN

ADDEN

FERR

OERR

RX9D

BAUDCON

—

RCIDL

—

SCKP

BRG16

—

WUE

ABDEN

SPBRGH

EUSART Baud Rate Generator Register High Byte

SPBRG

EUSART Baud Rate Generator Register Low Byte

Legend:

— = unimplemented, read as ‘0’. Shaded cells are not used by the BRG.

TABLE 20-3:

BAUD RATES FOR ASYNCHRONOUS MODES

BAUD

RATE

(K)

SYNC = 0, BRGH = 0, BRG16 = 0

FOSC = 40.000 MHz

FOSC = 20.000 MHz

FOSC = 10.000 MHz

FOSC = 8.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3

—

——

—

——

—

1.2

—

1.221

1.73

255

1.202

0.16

129

1.201

-0.16

103

2.4

2.441

1.73

255

2.404

0.16

129

2.404

0.16

2.403

-0.16

9.6

9.615

0.16

9.766

1.73

9.766

1.73

9.615

-0.16

19.2

19.531

1.73

19.531

1.73

19.531

1.73

—

57.6

56.818

-1.36

62.500

8.51

52.083

-9.58

—

115.2

125.000

8.51

104.167

-9.58

78.125

-32.18

—

BAUD

RATE

(K)

SYNC = 0, BRGH = 0, BRG16 = 0

FOSC = 4.000 MHz

FOSC = 2.000 MHz

FOSC = 1.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3

0.300

0.16

207

0.300

-0.16

103

0.300

-0.16

1.2

1.202

0.16

1.201

-0.16

1.201

-0.16

2.4

2.404

0.16

2.403

-0.16

—

9.6

8.929

-6.99

—

19.2

20.833

8.51

—

57.6

62.500

8.51

—

115.2

62.500

-45.75

—

For a device with FOSC of 16 MHz, desired baud rate of 9600, Asynchronous mode, 8-bit BRG:

Desired Baud Rate = FOSC/(64 ([SPBRGH:SPBRG] + 1))

Solving for SPBRGH:SPBRG:

((FOSC/Desired Baud Rate)/64) – 1

((16000000/9600)/64) – 1

[25.042] = 25

Calculated Baud Rate = 16000000/(64 (25 + 1))

9615

Error

(Calculated Baud Rate – Desired Baud Rate)/Desired Baud Rate

(9615 – 9600)/9600 = 0.16%

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