PIC16F882-I datasheet(203/328 Pages) MICROCHIP

203 / 328 page

DS41291F-page 201

PIC16F882/883/884/886/887

13.4.10

ACKNOWLEDGE SEQUENCE TIMING

An Acknowledge sequence is enabled by setting the

Acknowledge Sequence Enable bit, ACKEN (SSPCON2

and the contents of the Acknowledge Data bit (ACKDT)

is presented on the SDA pin. If the user wishes to gener-

ate an Acknowledge, then the ACKDT bit should be

cleared. If not, the user should set the ACKDT bit before

starting an Acknowledge sequence. The Baud Rate

Generator then counts for one rollover period (TBRG) and

the SCL pin is de-asserted (pulled high). When the SCL

pin is sampled high (clock arbitration), the Baud Rate

Generator counts for TBRG. The SCL pin is then pulled

low. Following this, the ACKEN bit is automatically

cleared, the Baud Rate Generator is turned off and the

MSSP module then goes into Idle mode (Figure 13-17).

13.4.10.1

WCOL Status Flag

If the user writes the SSPBUF when an Acknowledge

sequence is in progress, then WCOL is set and the

contents of the buffer are unchanged (the write doesn’t

occur).

13.4.11

STOP CONDITION TIMING

A Stop bit is asserted on the SDA pin at the end of a

receive/transmit by setting the Stop Sequence Enable

bit, PEN (SSPCON2 register). At the end of a receive/

transmit, the SCL line is held low after the falling edge

of the ninth clock. When the PEN bit is set, the master

will assert the SDA line low. When the SDA line is sam-

pled low, the Baud Rate Generator is reloaded and

counts down to 0. When the Baud Rate Generator

times out, the SCL pin will be brought high, and one

TBRG (Baud Rate Generator rollover count) later, the

SDA pin will be de-asserted. When the SDA pin is sam-

pled high while SCL is high, the P bit (SSPSTAT regis-

ter) is set. A TBRG later, the PEN bit is cleared and the

SSPIF bit is set (Figure 13-18).

13.4.11.1

WCOL Status Flag

If the user writes the SSPBUF when a Stop sequence

is in progress, then the WCOL bit is set and the

contents of the buffer are unchanged (the write doesn’t

occur).

FIGURE 13-17:

ACKNOWLEDGE SEQUENCE WAVEFORM

Note: TBRG = one Baud Rate Generator period.

SDA

SCL

Set SSPIF at the end

Acknowledge sequence starts here,

Write to SSPCON2

ACKEN automatically cleared

Cleared in

TBRG

of receive

ACK

ACKEN = 1, ACKDT = 0

SSPIF

software

Set SSPIF at the end

of Acknowledge sequence

Cleared in

software

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