PIC18F87J11_12 Datasheet, PDF (269/466 Pages) Microchip Technology – 64/80-Pin, High-Performance, 1-Mbit Flash Microcontrollers

20.4.6.1 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 SDAx while SCLx 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
contains 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 SDAx, while SCLx outputs
the serial clock. Serial data is received 8 bits at a time.
After each byte is received, an Acknowledge bit is
transmitted. Start and Stop conditions indicate the
beginning and end of transmission.
The Baud Rate Generator, used for the SPI mode
operation, is used to set the SCLx clock frequency for
either 100 kHz, 400 kHz or 1 MHz I²C operation. See
Section 20.4.7 “Baud Rate” for more details.
PIC18F87J11 FAMILY
A typical transmit sequence would go as follows:
1. The user generates a Start condition by setting
the Start Enable bit, SEN (SSPxCON2<0>).
2. SSPxIF is set. The MSSPx module will wait the
required start time before any other operation
takes place.
3. The user loads the SSPxBUF with the slave
address to transmit.
4. Address is shifted out of the SDAx pin until all
8 bits are transmitted.
5. The MSSPx module shifts in the ACK bit from
the slave device and writes its value into the
SSPxCON2 register (SSPxCON2<6>).
6. The MSSPx module generates an interrupt at
the end of the ninth clock cycle by setting the
SSPxIF bit.
7. The user loads the SSPxBUF with eight bits of
data.
8. Data is shifted out of the SDAx pin until all 8 bits
are transmitted.
9. The MSSPx module shifts in the ACK bit from
the slave device and writes its value into the
SSPxCON2 register (SSPxCON2<6>).
10. The MSSPx module generates an interrupt at
the end of the ninth clock cycle by setting the
SSPxIF bit.
11. The user generates a Stop condition by setting
the Stop Enable bit, PEN (SSPxCON2<2>).
12. Interrupt is generated once the Stop condition is
complete.
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DS39778E-page 269