PIC18F1XK22 Datasheet, PDF (162/388 Pages) Microchip Technology – 20-Pin Flash Microcontrollers with nanoWatt XLP Technology

PIC18F1XK22/LF1XK22
14.3.6.1 I²C Master Mode Operation
The master device generates all of the serial clock
pulses and the Start and Stop conditions. A transfer is
ended with a Stop condition or with a Repeated Start
condition. Since the Repeated Start condition is also
the beginning of the next serial transfer, the I²C bus will
not be released.
In Master Transmitter mode, serial data is output
through SDA, while SCL outputs the serial clock. The
first byte transmitted contains the slave address of the
receiving device (7 bits) and the Read/Write (R/W) bit.
In this case, the R/W bit will be logic ‘0’. Serial data is
transmitted 8 bits at a time. After each byte is transmit-
ted, an Acknowledge bit is received. Start and Stop
conditions are output to indicate the beginning and the
end of a serial transfer.
In Master Receive mode, the first byte transmitted con-
tains the slave address of the transmitting device
(7 bits) and the R/W bit. In this case, the R/W bit will be
logic ‘1’. Thus, the first byte transmitted is a 7-bit slave
address followed by a ‘1’ to indicate the receive bit.
Serial data is received via SDA, while SCL outputs the
serial clock. Serial data is received 8 bits at a time. After
each byte is received, an Acknowledge bit is transmit-
ted. Start and Stop conditions indicate the beginning
and end of transmission.
A Baud Rate Generator is used to set the clock
frequency output on SCL. See Section 14.3.7 “Baud
Rate” for more detail.
A typical transmit sequence would go as follows:
1. The user generates a Start condition by setting
the SEN bit of the SSPCON2 register.
2. SSPIF is set. The MSSP module will wait the
required start time before any other operation
takes place.
3. The user loads the SSPBUF with the slave
address to transmit.
4. Address is shifted out the SDA pin until all 8 bits
are transmitted.
5. The MSSP module shifts in the ACK bit from the
slave device and writes its value into the
ACKSTAT bit of the SSPCON2 register.
6. The MSSP module generates an interrupt at the
end of the ninth clock cycle by setting the SSPIF
bit.
7. The user loads the SSPBUF with eight bits of
data.
8. Data is shifted out the SDA pin until all 8 bits are
transmitted.
9. The MSSP module shifts in the ACK bit from the
slave device and writes its value into the
ACKSTAT bit of the SSPCON2 register.
10. The MSSP module generates an interrupt at the
end of the ninth clock cycle by setting the SSPIF
bit.
11. The user generates a Stop condition by setting
the PEN bit of the SSPCON2 register.
12. Interrupt is generated once the Stop condition is
complete.
DS41365D-page 162
Preliminary
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