PIC18F23K20-ESLASHML datasheet(202/456 Pages) MICROCHIP

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PIC18F2XK20/4XK20

DS41303G-page 202

 2010 Microchip Technology Inc.

17.4

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) – SCK/SCL

• Serial data (SDA) – SDI/SDA

The user must configure these pins as inputs with the

corresponding TRIS bits.

FIGURE 17-7:

MSSP BLOCK DIAGRAM

(I2C™ MODE)

17.4.1

REGISTERS

The MSSP module has seven 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)

• MSSP Address Mask (SSPMSK)

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 6 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.

When the SSP is configured in Master mode, the lower

seven bits of SSPADD act as the Baud Rate Generator

reload value. When the SSP is configured for I2C slave

mode the SSPADD register holds the slave device

address. The SSP can be configured to respond to a

range of addresses by qualifying selected bits of the

address register with the SSPMSK register.

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

not

double-buffered. A write to SSPBUF will write to both

SSPBUF and SSPSR.

Read

Write

SSPSR Reg

Match Detect

SSPADD Reg

Start and

Stop bit Detect

SSPBUF Reg

Internal

Data Bus

Addr Match

Set, Reset

S, P bits

(SSPSTAT Reg)

SCK/SCL

SDI/SDA

Shift

Clock

MSb

LSb

SSPMSK Reg

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