PIC18F2221 MICROCHIP [Microchip Technology], PIC18F2221 Datasheet - Page 200

• Manufacturer Part Number: PIC18F2221
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F4321 FAMILY
17.4.12
An Acknowledge sequence is enabled by setting the
Acknowledge
(SSPCON2<4>). When this bit is set, the SCL pin is
pulled low and the contents of the Acknowledge data bit
are presented on the SDA pin. If the user wishes to gen-
erate 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 (T
and the SCL pin is deasserted (pulled high). When the
SCL pin is sampled high (clock arbitration), the Baud
Rate Generator counts for T
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 17-25).
17.4.12.1
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).
FIGURE 17-25:
FIGURE 17-26:
DS39689E-page 198
Note: T
ACKNOWLEDGE SEQUENCE
TIMING
WCOL Status Flag
Note: T
SSPIF
Sequence
SCL
SDA
BRG
Acknowledge sequence starts here,
SDA
SCL
Write to SSPCON2,
Falling edge of
9th clock
BRG
= one Baud Rate Generator period.
ACKNOWLEDGE SEQUENCE WAVEFORM
STOP CONDITION RECEIVE OR TRANSMIT MODE
SSPIF set at
the end of receive
= one Baud Rate Generator period.
ACK
ACKEN = 1, ACKDT = 0
BRG
Enable
set PEN
. The SCL pin is then
write to SSPCON2
bit,
8
SDA asserted low before rising edge of clock
to setup Stop condition
D0
T
T
BRG
BRG
ACKEN
BRG
Preliminary
T
SCL brought high after T
)
BRG
Cleared in
software
T
BRG
P
ACK
SCL = 1 for T
after SDA sampled high. P bit (SSPSTAT<4>) is set.
T
17.4.13
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<2>). 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
sampled 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
T
SDA pin will be deasserted. When the SDA pin is
sampled high while SCL is high, the P bit
(SSPSTAT<4>) is set. A T
cleared and the SSPIF bit is set (Figure 17-26).
17.4.13.1
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).
BRG
BRG
T
BRG
9
SSPIF set at the end
of Acknowledge sequence
(Baud Rate Generator rollover count) later, the
PEN bit (SSPCON2<2>) is cleared by
hardware and the SSPIF bit is set
BRG
BRG
STOP CONDITION TIMING
, followed by SDA = 1 for T
ACKEN automatically cleared
WCOL Status Flag
Cleared in
software
© 2007 Microchip Technology Inc.
BRG
later, the PEN bit is
BRG