PIC18F2480/2580/4480/4580
EXAMPLE 19-1:
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
16000000/(64 (25 + 1))
9615
Calculated Baud Rate
Error
(Calculated Baud Rate – Desired Baud Rate)/Desired Baud Rate
(9615 – 9600)/9600 = 0.16%
TABLE 19-2: REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR
Reset
Values
on Page:
Name
TXSTA
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
CSRC
SPEN
TX9
RX9
TXEN
SREN
—
SYNC
CREN
SCKP
SENDB
ADDEN
BRG16
BRGH
FERR
—
TRMT
OERR
WUE
TX9D
RX9D
57
57
57
57
57
RCSTA
BAUDCON
SPBRGH
SPBRG
ABDOVF RCIDL
ABDEN
EUSART Baud Rate Generator Register High Byte
EUSART Baud Rate Generator Register Low Byte
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the BRG.
DS39637D-page 236
© 2009 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
