Datasheet
2010-2012 Microchip Technology Inc. DS41419D-page 291
PIC16(L)F1824/1828
25.7 Baud Rate Generator
The MSSP1 module has a Baud Rate Generator avail-
able for clock generation in both I
2
C and SPI Master
modes. The Baud Rate Generator (BRG) reload value
is placed in the SSP1ADD register (Register 25-6).
When a write occurs to SSP1BUF, the Baud Rate Gen-
erator will automatically begin counting down.
Once the given operation is complete, the internal clock
will automatically stop counting and the clock pin will
remain in its last state.
An internal signal “Reload” in Figure 25-40 triggers the
value from SSP1ADD to be loaded into the BRG
counter. This occurs twice for each oscillation of the
module clock line. The logic dictating when the reload
signal is asserted depends on the mode the MSSP1 is
being operated in.
Table 25-4 demonstrates clock rates based on
instruction cycles and the BRG value loaded into
SSP1ADD.
EQUATION 25-1:
FIGURE 25-40: BAUD RATE GENERATOR BLOCK DIAGRAM
TABLE 25-4: MSSP1 CLOCK RATE W/BRG
25.7.1 ALTERNATE PIN LOCATIONS
This module incorporates I/O pins that can be moved to
other locations with the use of the alternate pin function
registers, APFCON0 and APFCON1. To determine
which pins can be moved and what their default loca-
tions are upon a Reset, see Section 12.1 “Alternate
Pin Function” for more information.
FCLOCK
FOSC
SSPxADD 1+4
-------------------------------------------------=
Note: Values of 0x00, 0x01 and 0x02 are not valid
for SSP1ADD when used as a Baud Rate
Generator for I
2
C. This is an implementation
limitation.
F
OSC FCY BRG Value
F
CLOCK
(2 Rollovers of BRG)
32 MHz 8 MHz 13h 400 kHz
(1)
32 MHz 8 MHz 19h 308 kHz
32 MHz 8 MHz 4Fh 100 kHz
16 MHz 4 MHz 09h 400 kHz
(1)
16 MHz 4 MHz 0Ch 308 kHz
16 MHz 4 MHz 27h 100 kHz
4 MHz 1 MHz 09h 100 kHz
Note 1: The I
2
C interface does not conform to the 400 kHz I
2
C specification (which applies to rates greater than
100 kHz) in all details, but may be used with care where higher rates are required by the application.
SSP1M<3:0>
BRG Down Counter
SSP1CLK
F
OSC/2
SSP1ADD<7:0>
SSP1M<3:0>
SCL
Reload
Control
Reload