PIC16F720-ESLASHML datasheet(139/244 Pages) MICROCHIP

139 / 244 page

 2010 Microchip Technology Inc.

DS41430A-page 139

PIC16F/LF720/721

17.0

SSP MODULE OVERVIEW

The Synchronous Serial Port (SSP) module is a serial

interface useful for communicating with other peripher-

als or microcontroller devices. These peripheral

devices may be serial EEPROMs, shift registers, dis-

play drivers, A/D converters, etc. The SSP module can

operate in one of two modes:

• Serial Peripheral Interface (SPI)

• Inter-Integrated Circuit (I2C™)

17.1

SPI Mode

The SPI mode allows 8 bits of data to be synchronously

transmitted and received, simultaneously. The SSP

module can be operated in one of two SPI modes:

•Master mode

• Slave mode

SPI is a full-duplex protocol, with all communication

being bidirectional and initiated by a master device. All

clocking is provided by the master device and all bits

are transmitted, MSb first. Care must be taken to

ensure that all devices on the SPI bus are setup to

allow all controllers to send and receive data at the

same time.

A typical SPI connection between microcontroller

devices is shown in Figure 17-1. Addressing of more

than one slave device is accomplished via multiple

hardware slave select lines. External hardware and

additional I/O pins must be used to support multiple

slave select addressing. This prevents extra overhead

in software for communication.

For SPI communication, typically three pins are used:

• Serial Data Out (SDO)

• Serial Data In (SDI)

• Serial Clock (SCK)

Additionally, a fourth pin may be used when in a Slave

mode of operation:

• Slave Select (SS)

FIGURE 17-1:

TYPICAL SPI MASTER/SLAVE CONNECTION

Serial Input Buffer

(SSPBUF)

Shift Register

(SSPSR)

MSb

LSb

SDO

SDI

Processor 1

SCK

SPI Master SSPM<3:0> = 00xx

Serial Input Buffer

(SSPBUF)

Shift Register

(SSPSR)

LSb

MSb

SDI

SDO

Processor 2

SCK

SPI Slave SSPM<3:0> = 010x

Serial Clock

Slave Select

General I/O

(optional)

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