PIC16C923T-08I/SP View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16C923T-08I/SP

8-Bit CMOS Microcontroller with LCD Driver

Microchip Technology 

11.3 SSP I2C Operation

The SSP module in I2C mode fully implements all slave

functions, except general call support, and provides

interrupts on start and stop bits in hardware to facilitate

firmware implementations of the master functions. The

SSP module implements the standard mode specifica-

tions as well as 7-bit and 10-bit addressing. Two pins

are used for data transfer. These are the RC3/SCK/SCL

pin, which is the clock (SCL), and the RC4/SDI/SDA

pin, which is the data (SDA). The user must configure

these pins as inputs or outputs through the

TRISC<4:3> bits. The SSP module functions are

enabled by setting SSP Enable bit SSPEN (SSP-

CON<5>).

FIGURE 11-18: SSP BLOCK DIAGRAM

(I2C MODE)

Read

Internal

data bus

Write

RC3/SCK/SCL

SSPBUF reg

RC4/

SDI/

SDA

shift

clock

SSPSR reg

MSb

LSb

Match detect

Addr Match

SSPADD reg

Start and

Stop bit detect

Set, Reset

S, P bits

(SSPSTAT reg)

The SSP module has five registers for I2C operation.

These are the:

• SSP Control Register (SSPCON)

• SSP Status Register (SSPSTAT)

• Serial Receive/Transmit Buffer (SSPBUF)

• SSP Shift Register (SSPSR) - Not directly acces-

sible

• SSP Address Register (SSPADD)

PIC16C9XX

The SSPCON register allows control of the I2C opera-

tion. Four mode selection bits (SSPCON<3:0>) allow

one of the following I2C modes to be selected:

• I2C Slave mode (7-bit address)

• I2C Slave mode (10-bit address)

• I2C Slave mode (7-bit address), with start and

stop bit interrupts enabled

• I2C Slave mode (10-bit address), with start and

stop bit interrupts enabled

• I2C Firmware controlled Master Mode, slave is

idle

Selection of any I2C mode, with the SSPEN bit set,

forces the SCL and SDA pins to be open drain, pro-

vided these pins are programmed to inputs by setting

the appropriate TRISC bits.

The SSPSTAT register gives the status of the data

transfer. This information includes detection of a START

or STOP bit, specifies if the received byte was data or

address if the next byte is the completion of 10-bit

address, and if this will be a read or write data transfer.

The SSPSTAT register is read only.

The SSPBUF is the register to which transfer data is

written to or read from. The SSPSR register shifts the

data in or out of the device. In receive operations, the

SSPBUF and SSPSR create a doubled buffered

receiver. This allows reception of the next byte to begin

before reading the last byte of received data. When the

complete byte is received, it is transferred to the

SSPBUF register and flag bit SSPIF is set. If another

complete byte is received before the SSPBUF register

is read, a receiver overflow has occurred and bit

SSPOV (SSPCON<6>) is set and the byte in the

SSPSR is lost.

The SSPADD register holds the slave address. In 10-bit

mode, the user needs to write the high byte of the

address (1111 0 A9 A8 0). Following the high byte

address match, the low byte of the address needs to be

loaded (A7:A0).

© 1997 Microchip Technology Inc.

DS30444E - page 73

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