PIC16F193X Datasheet, PDF (322/418 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt Technology

PIC16F193X/LF193X
22.7 BAUD RATE GENERATOR
The MSSP module has a Baud Rate Generator avail-
able for clock generation in both I²C and SPI Master
modes. The Baud Rate Generator (BRG) reload value
is placed in the SSPADD register (Register 22-6).
When a write occurs to SSPBUF, 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 22-36 triggers the
value from SSPADD 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 MSSP is being
operated in.
Table 22-3 demonstrates clock rates based on
instruction cycles and the BRG value loaded into
SSPADD.
EQUATION 22-1:
FCLOCK = ₍---S---S----P----A----FD---^O-D---^S--^C-+------1---₎---₍--4----₎
FIGURE 22-37: BAUD RATE GENERATOR BLOCK DIAGRAM
SSPM<3:0>
SSPADD<7:0>
SSPM<3:0>
SCL
Reload
Control
Reload
SSPCLK
BRG Down Counter
FOSC/2
Note:
Values of 0x00, 0x01 and 0x02 are not valid
for SSPADD when used as a Baud Rate
Generator for I²C. This is an implementation
limitation.
TABLE 22-3: MSSP CLOCK RATE W/BRG
FOSC
FCY
BRG Value
FCLOCK
(2 Rollovers of BRG)
32 MHz
8 MHz
13h
400 kHz⁽¹⁾
32 MHz
8 MHz
19h
308 kHz
32 MHz
16 MHz
8 MHz
4 MHz
4Fh
100 kHz
09h
400 kHz⁽¹⁾
16 MHz
4 MHz
0Ch
308 kHz
16 MHz
4 MHz
27h
100 kHz
Note 1:
4 MHz
1 MHz
09h
100 kHz
4 MHz
1 MHz
00h
250 kHz⁽²⁾
The I²C interface does not conform to the 400 kHz I²C 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.
2: SPI mode only.
DS41364A-page 320
Preliminary
© 2008 Microchip Technology Inc.