Datasheet

PIC18F47J13 FAMILY
DS39974A-page 310 Preliminary  2010 Microchip Technology Inc.
20.5 I
2
C Mode
The MSSP module in I
2
C 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 and 7-bit and 10-bit addressing.
Two pins are used for data transfer:
• Serial Clock (SCLx) – RC3/SCK1/SCL1/RP14,
RD0/PMD0/SCL2 (44-pin devices) or
RB4/CCP4/PMA1/KBI0/SCL2/RP7
(28-pin devices)
• Serial Data (SDAx) – RC4/SDI1/SDA1/RP15,
RD1/PMD1/SDA2 (44-pin devices) or
RB5/CCP5/KBI1/SDA2/RP8 (28-pin devices)
The user must configure these pins as inputs by setting
the associated TRISx bits. These pins are up to 5.5V
tolerant, allowing direct use in I
2
C busses operating at
voltages higher than V
DD.
FIGURE 20-7: MSSPx BLOCK DIAGRAM
(I
2
C™ MODE)
20.5.1 REGISTERS
The MSSP module has six registers for I
2
C operation.
These are:
• MSSPx Control Register 1 (SSPxCON1)
• MSSPx Control Register 2 (SSPxCON2)
• MSSPx Status Register (SSPxSTAT)
• Serial Receive/Transmit Buffer Register
(SSPxBUF)
• MSSPx Shift Register (SSPxSR) – Not directly
accessible
• MSSPx Address Register (SSPxADD)
• MSSPx 7-Bit Address Mask Register (SSPxMSK)
SSPxCON1, SSPxCON2 and SSPxSTAT are the
control and status registers in I
2
C mode operation. The
SSPxCON1 and SSPxCON2 registers are readable and
writable. The lower six bits of the SSPxSTAT are
read-only. The upper two bits of the SSPxSTAT are
read/write.
SSPxSR is the shift register used for shifting data in or
out. SSPxBUF is the buffer register to which data
bytes are written to or read from.
SSPxADD contains the slave device address when the
MSSP is configured in I
2
C Slave mode. When the
MSSP is configured in Master mode, the lower seven
bits of SSPxADD act as the Baud Rate Generator
(BRG) reload value.
SSPxMSK holds the slave address mask value when
the module is configured for 7-Bit Address Masking
mode. While it is a separate register, it shares the same
SFR address as SSPxADD; it is only accessible when
the SSPM<3:0> bits are specifically set to permit
access. Additional details are provided in
Section 20.5.3.4 “7-Bit Address Masking Mode”.
In receive operations, SSPxSR and SSPxBUF
together, create a double-buffered receiver. When
SSPxSR receives a complete byte, it is transferred to
SSPxBUF and the SSPxIF interrupt is set.
During transmission, the SSPxBUF is not
double-buffered. A write to SSPxBUF will write to both
SSPxBUF and SSPxSR.
Read Write
SSPxSR reg
Match Detect
SSPxADD reg
SSPxBUF reg
Internal
Data Bus
Addr Match
Set, Reset
S, P bits
(SSPxSTAT reg)
Shift
Clock
MSb
LSb
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.
SCLx
SDAx
Start and
Stop bit Detect
Address Mask