PIC16LF18854 Datasheet, PDF (472/668 Pages) Microchip Technology – C Compiler Optimized RISC Architecture

PIC16(L)F18856/76
31.4.5 START CONDITION
The I²C specification defines a Start condition as a
transition of SDA from a high to a low state while SCL
line is high. A Start condition is always generated by
the master and signifies the transition of the bus from
an Idle to an Active state. Figure 31-12 shows wave
forms for Start and Stop conditions.
A bus collision can occur on a Start condition if the
module samples the SDA line low before asserting it
low. This does not conform to the I²C Specification that
states no bus collision can occur on a Start.
31.4.6 STOP CONDITION
A Stop condition is a transition of the SDA line from
low-to-high state while the SCL line is high.
Note: At least one SCL low time must appear
before a Stop is valid, therefore, if the SDA
line goes low then high again while the SCL
line stays high, only the Start condition is
detected.
31.4.7 RESTART CONDITION
A Restart is valid any time that a Stop would be valid.
A master can issue a Restart if it wishes to hold the
bus after terminating the current transfer. A Restart
has the same effect on the slave that a Start would,
resetting all slave logic and preparing it to clock in an
address. The master may want to address the same or
another slave. Figure 31-13 shows the wave form for a
Restart condition.
In 10-bit Addressing Slave mode a Restart is required
for the master to clock data out of the addressed
slave. Once a slave has been fully addressed, match-
ing both high and low address bytes, the master can
issue a Restart and the high address byte with the
R/W bit set. The slave logic will then hold the clock
and prepare to clock out data.
After a full match with R/W clear in 10-bit mode, a prior
match flag is set and maintained until a Stop condition, a
high address with R/W clear, or high address match fails.
31.4.8 START/STOP CONDITION INTERRUPT
MASKING
The SCIE and PCIE bits of the SSPxCON3 register
can enable the generation of an interrupt in Slave
modes that do not typically support this function. Slave
modes where interrupt on Start and Stop detect are
already enabled, these bits will have no effect.
FIGURE 31-12: I²C START AND STOP CONDITIONS
SDA
SCL
S
Start
Condition
Change of
Data Allowed
FIGURE 31-13: I²C RESTART CONDITION
Change of
Data Allowed
P
Stop
Condition
DS40001824A-page 472
Change of
Data Allowed
Sr
Restart
Condition
Change of
Data Allowed
Preliminary
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