PIC24FJ128GA MICROCHIP [Microchip Technology], PIC24FJ128GA Datasheet - Page 134

• Manufacturer Part Number: PIC24FJ128GA
• Description: General Purpose, 16-Bit Flash Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

PIC24FJ128GA FAMILY
16.1
The UART module includes a dedicated 16-bit Baud
Rate Generator. The BRGx register controls the period
of a free-running 16-bit timer. Equation 16-1 shows the
formula for computation of the baud rate with
BRGH = 0.
EQUATION 16-1:
Example 16-1 shows the calculation of the baud rate
error for the following conditions:
• F
• Desired Baud Rate = 9600
EXAMPLE 16-1:
DS39747C-page 132
Note 1: Based on T
Desired Baud Rate
Solving for BRGx value:
Calculated Baud Rate = 4000000/(16 (25 + 1))
Error
Note 1: F
CY
= 4 MHz
UART Baud Rate Generator (BRG)
2: Based on T
BRGx
BRGx
BRGx
Baud Rate =
BRGx =
frequency (F
and PLL are disabled.
CY
denotes the instruction cycle clock
= F
= ((F
= ((4000000/9600)/16) – 1
= 25
= 9615
= (Calculated Baud Rate – Desired Baud Rate)
= (9615 – 9600)/9600
= 0.16%
UART BAUD RATE WITH
BAUD RATE ERROR CALCULATION (BRGH = 0)
CY
BRGH = 0
Desired Baud Rate
CY
16 • (BRGx + 1)
16 • Baud Rate
CY
OSC
= F
CY
/(16 (BRGx + 1))
= F
OSC
/Desired Baud Rate)/16) – 1
/2).
F
F
CY
CY
OSC
/2, Doze mode and PLL are disabled.
(1,2)
/2, Doze mode
– 1
Preliminary
The maximum baud rate (BRGH = 0) possible is
F
possible is F
Equation 16-2 shows the formula for computation of
the baud rate with BRGH = 1.
EQUATION 16-2:
The maximum baud rate (BRGH = 1) possible is F
(for BRGx = 0) and the minimum baud rate possible is
F
Writing a new value to the BRGx register causes the
BRG timer to be reset (cleared). This ensures the BRG
does not wait for a timer overflow before generating the
new baud rate.
CY
CY
Note 1: F
/16 (for BRGx = 0), and the minimum baud rate
/(4 * 65536).
2: Based on T
Baud Rate =
BRGx =
CY
frequency.
and PLL are disabled.
CY
/(16 * 65536).
(1)
denotes the instruction cycle clock
UART BAUD RATE WITH
BRGH = 1
© 2006 Microchip Technology Inc.
CY
4 • (BRGx + 1)
4 • Baud Rate
= F
F
F
CY
CY
OSC
(1,2)
/2, Doze mode
– 1
CY
/4