PIC16F1459-ESSQTP datasheet(217/418 Pages) MICROCHIP

217 / 418 page

 2012 Microchip Technology Inc.

Preliminary

DS41639A-page 217

PIC16(L)F1454/5/9

22.4.5

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 22-12 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.

22.4.6

STOP CONDITION

A Stop condition is a transition of the SDA line from

low-to-high state while the SCL line is high.

22.4.7

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 22-13 shows wave forms 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 condi-

tion, a high address with R/W clear, or high address

match fails.

22.4.8

START/STOP CONDITION INTERRUPT

MASKING

The SCIE and PCIE bits of the SSPCON3 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 22-12:

I2C START AND STOP CONDITIONS

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.

SDA

SCL

Stop

Condition

Start

Condition

Change of

Data Allowed

Change of

Data Allowed

PIC16F1459-ESSQTP Datasheet(PDF) 217 Page - Microchip Technology

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