PIC18F4550-IP Datasheet, PDF (209/438 Pages) Microchip Technology – 28/40/44-Pin, High-Performance, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

PIC18F2455/2550/4455/4550
19.4 I²C Mode
The MSSP module in I²C mode fully implements all
master and slave functions (including general call
support) and provides interrupts on Start and Stop bits
in hardware to determine a free bus (multi-master
function). The MSSP module implements the standard
mode specifications, as well as 7-bit and 10-bit
addressing.
Two pins are used for data transfer:
• Serial clock (SCL) – RB1/AN10/INT1/SCK/SCL
• Serial data (SDA) – RB0/AN12/INT0/FLT0/SDI/SDA
The user must configure these pins as inputs by setting
the associated TRIS bits.
FIGURE 19-7:
MSSP BLOCK DIAGRAM
(I²C™ MODE)
Read
Internal
Data Bus
Write
SCL
SDA
SSPBUF reg
Shift
Clock
SSPSR reg
MSb
LSb
Match Detect
Address Mask
Addr Match
SSPADD reg
19.4.1 REGISTERS
The MSSP module has six registers for I²C operation.
These are:
• MSSP Control Register 1 (SSPCON1)
• MSSP Control Register 2 (SSPCON2)
• MSSP Status Register (SSPSTAT)
• Serial Receive/Transmit Buffer Register
(SSPBUF)
• MSSP Shift Register (SSPSR) – Not directly
accessible
• MSSP Address Register (SSPADD)
SSPCON1, SSPCON2 and SSPSTAT are the control
and status registers in I²C mode operation. The
SSPCON1 and SSPCON2 registers are readable and
writable. The lower six bits of the SSPSTAT are read-only.
The upper two bits of the SSPSTAT are read/write.
SSPSR is the shift register used for shifting data in or
out. SSPBUF is the buffer register to which data bytes
are written to or read from.
SSPADD register holds the slave device address when
the MSSP is configured in I²C Slave mode. When the
MSSP is configured in Master mode, the lower seven
bits of SSPADD act as the Baud Rate Generator reload
value.
In receive operations, SSPSR and SSPBUF together
create a double-buffered receiver. When SSPSR
receives a complete byte, it is transferred to SSPBUF
and the SSPIF interrupt is set.
During transmission, the SSPBUF is not double-
buffered. A write to SSPBUF will write to both SSPBUF
and SSPSR.
Start and
Stop bit Detect
Set, Reset
S, P bits
(SSPSTAT reg)
Note: Only port I/O names are used in this diagram for
the sake of brevity. Refer to the text for a full list of
multiplexed functions.
© 2009 Microchip Technology Inc.
DS39632E-page 207