PIC16F872 Datasheet, PDF (75/160 Pages) Microchip Technology – 28-Pin, 8-Bit CMOS FLASH Microcontroller

PIC16F872
9.2.13 ACKNOWLEDGE SEQUENCE TIMING
An acknowledge sequence is enabled by setting the
acknowledge sequence enable bit, ACKEN
(SSPCON2<4>). When this bit is set, the SCL pin is
pulled low and the contents of the acknowledge data
bit is presented on the SDA pin. If the user wishes to
generate an acknowledge, 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 deasserted (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 auto-
matically cleared, the baud rate generator is turned off,
and the SSP module then goes into IDLE mode.
(Figure 9-16)
9.2.13.13 WCOL STATUS FLAG
If the user writes the SSPBUF when an acknowledege
sequence is in progress, the WCOL is set and the con-
tents of the buffer are unchanged (the write doesn’t
occur).
FIGURE 9-16: ACKNOWLEDGE SEQUENCE WAVEFORM
Acknowledge sequence starts here,
Write to SSPCON2
ACKEN = 1, ACKDT = 0
ACKEN automatically cleared
SDA
TBRG
TBRG
D0
ACK
SCL
8
9
SSPIF
Set SSPIF at the end
of receive
Cleared in
software
Note: TBRG = one baud rate generator period.
Cleared in
software
Set SSPIF at the end
of acknowledge sequence
© 1999 Microchip Technology Inc.
Preliminary
DS30221A-page 75