Datasheet

PIC18F2450/4450

EXAMPLE 15-1: CALCULATING BAUD RATE ERROR

TABLE 15-2: 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 51

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 51

BAUDCON ABDOVF RCIDL — SCKP BRG16 — WUE ABDEN 51

SPBRGH EUSART Baud Rate Generator Register High Byte 50

SPBRG EUSART Baud Rate Generator Register Low Byte 50

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

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

Desired Baud Rate = F

OSC/(64 ([SPBRGH:SPBRG] + 1)

Solving for SPBRGH:SPBRG:

X = ((F

OSC/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%