PIC16F946-ESLASHMLQTP datasheet(208/330 Pages) MICROCHIP

208 / 330 page

PIC16F913/914/916/917/946

DS41250F-page 206

14.12.3

TRANSMISSION

When the R/W bit of the incoming address byte is set

and an address match occurs, the R/W bit of the

SSPSTAT register is set. The received address is

loaded into the SSPBUF register. The ACK pulse will

sent

the

ninth

bit,

and

RC6/TX/CK/SCK/SCL/SEG9 is held low. The transmit

data must be loaded into the SSPBUF register, which

also

loads

the

SSPSR

Then,

RC6/TX/CK/SCK/SCL/SEG9 should be enabled by

setting bit CKP of the SSPCON register. The master

must monitor the SCL pin prior to asserting another

clock pulse. The slave devices may be holding off the

master by stretching the clock. The eight data bits are

shifted out on the falling edge of the SCL input. This

ensures that the SDA signal is valid during the SCL high

time (Figure 14-10).

An SSP interrupt is generated for each data transfer

byte. Flag bit SSPIF must be cleared in software, and

the SSPSTAT register is used to determine the status

of the byte. Flag bit SSPIF is set on the falling edge of

the ninth clock pulse.

As a slave-transmitter, the ACK pulse from the master

receiver is latched on the rising edge of the ninth SCL

input pulse. If the SDA line was high (not ACK), then

the data transfer is complete. When the ACK is latched

by the slave, the slave logic is reset (resets SSPSTAT

occurrence of the Start bit. If the SDA line was low

(ACK), the transmit data must be loaded into the

SSPBUF register, which also loads the SSPSR

be enabled by setting bit CKP.

FIGURE 14-10:

I2C™ WAVEFORMS FOR TRANSMISSION (7-BIT ADDRESS)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

CKP (SSPCON<4>)

ACK

Transmitting Data

R/W = 1

Receiving Address

56789

123

Cleared in software

SSPBUF is written in software

From SSP Interrupt

Service Routine

Set bit after writing to SSPBUF

Data in

sampled

SCL held low

while CPU

responds to SSPIF

(the SSPBUF must be written to

before the CKP bit can be set)

PIC16F946-E/MLQTP Datasheet(PDF) 208 Page - Microchip Technology

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