PIC16F872
9.2.15 CLOCK ARBITRATION
9.2.16 SLEEP OPERATION
Clock arbitration occurs when the master, during any
receive, transmit, or repeated start/stop condition,
deasserts 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).
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
SDA
SCL line sampled once every machine cycle (TOSC • 4).
Hold off BRG until SCL is sampled high.
TBRG
TBRG
TBRG
1999 Microchip Technology Inc.
Preliminary
DS30221A-page 77
MICROCHIP [ MICROCHIP ]
