PIC16F872_06 Datasheet, PDF (74/168 Pages) Microchip Technology – 28-Pin, 8-Bit CMOS Flash Microcontroller with 10-Bit A/D

PIC16F872
FIGURE 9-17:
STOP CONDITION RECEIVE OR TRANSMIT MODE
Write to SSPCON2,
set PEN
Falling edge of
9th clock
SCL
TBRG
SCL = 1 for TBRG, followed by SDA = 1 for TBRG
after SDA sampled high. P bit (SSPSTAT<4>) is set.
PEN bit (SSPCON2<2>) is cleared by
hardware and the SSPIF bit is set
SDA
ACK
TBRG
P
TBRG
TBRG
SCL brought high after TBRG
SDA asserted low before rising edge of clock
to setup STOP condition.
Note: TBRG = one baud rate generator period.
9.2.15 CLOCK ARBITRATION
Clock arbitration occurs when the master, during any
receive, transmit, or Repeated START/STOP condi-
tion, de-asserts the SCL pin (SCL allowed to float high).
When the SCL pin is allowed to float high, the baud rate
generator (BRG) is suspended from counting until the
SCL pin is actually sampled high. When the SCL pin is
sampled high, the baud rate generator is reloaded with
the contents of SSPADD<6:0> and begins counting.
This ensures that the SCL high time will always be at
least one BRG rollover count, in the event that the clock
is held low by an external device (Figure 9-18).
9.2.16 SLEEP OPERATION
While in SLEEP mode, the I²C module can receive
addresses or data, and when an address match or
complete byte transfer occurs, wake the processor
from SLEEP (if the SSP interrupt is enabled).
9.2.17 EFFECTS OF A RESET
A RESET disables the SSP module and terminates the
current transfer.
FIGURE 9-18:
CLOCK ARBITRATION TIMING IN MASTER TRANSMIT MODE
BRG overflow,
release SCL.
If SCL = 1, load BRG with
SSPADD<6:0> and start count
to measure high time interval.
BRG overflow occurs,
release SCL. Slave device holds SCL low.
SCL = 1, BRG starts counting
clock high interval
SCL
SCL line sampled once every machine cycle (TOSC • 4).
Hold off BRG until SCL is sampled high.
SDA
TBRG
TBRG
TBRG
DS30221C-page 72
© 2006 Microchip Technology Inc.