PIC18F2455_09 Datasheet, PDF (250/438 Pages) Microchip Technology – 28/40/44-Pin,High-Performance,Enhanced Flash,USB Microcontrollers with nanoWatt Technology

PIC18F2455/2550/4455/4550
EXAMPLE 20-1: CALCULATING BAUD RATE ERROR
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:
X = ((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%
TABLE 20-2: REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2 Bit 1
TXSTA
CSRC
TX9
TXEN SYNC SENDB BRGH TRMT
RCSTA
SPEN
RX9
SREN CREN ADDEN FERR OERR
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16
—
WUE
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.
Bit 0
TX9D
RX9D
ABDEN
Reset Values
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DS39632E-page 248
© 2009 Microchip Technology Inc.