Microchip Technology MA330025-1 Data Sheet

 2009-2012 Microchip Technology Inc.

DS70616G-page 337

The SPI module is a synchronous serial interface use-
ful for communicating with other peripheral or micro-
controller devices. These peripheral devices can be
serial EEPROMs, shift registers, display drivers, ADC
Converters, etc. The SPI module is compatible with the
Motorola

®

 SPI and SIOP interfaces.

Four SPI modules are provided on a single device.
These modules, which are designated as SPI1, SPI2,
SPI3 and SPI4, are functionally identical with the excep-
tion that SPI2 is not remappable. The dedicated SDI2,
SDO2 and SCK2 connections provide improved perfor-
mance over SPI1, SPI3 and SPI4 (see 

). Each SPI module

includes an eight-word FIFO buffer and allows DMA bus
connections. When using the SPI module with DMA,
FIFO operation can be disabled.

The SPIx serial interface consists of four pins, as
follows:
• SDIx: Serial Data Input
• SDOx: Serial Data Output
• SCKx: Shift Clock Input or Output
• SSx/FSYNCx: Active-Low Slave Select or Frame 

Synchronization I/O Pulse

The SPIx module can be configured to operate with
two, three or four pins. In 3-pin mode, SSx is not used.
In 2-pin mode, neither SDOx nor SSx is used. 

 illustrates the block diagram of the SPI

module in Standard and Enhanced modes.

Note 1: This data sheet summarizes the features

of the dsPIC33EPXXX(GP/MC/MU)806/
810/814 and PIC24EPXXX(GP/GU)810/
814 families of devices. It is not intended
to be a comprehensive reference source.
To complement the information in this
data sheet, refer to Section 18. “Serial
Peripheral Interface (SPI)” (DS70569)
of the “dsPIC33E/PIC24E Family
Reference Manual”, which is available
from the Microchip web site
(

www.microchip.com

).

2: Some registers and associated bits

described in this section may not be
available on all devices. Refer to

 in

this data sheet for device-specific register
and bit information.

In this section, the SPI modules are
referred to together as SPIx, or separately
as SPI1, SPI2, SPI3 and SPI4. Special
Function Registers follow a similar nota-
tion. For example, SPIxCON refers to the
control register for the SPI1, SPI2, SPI3
or SPI4 module.

Internal Data Bus

SDIx

SDOx

SSx/FSYNCx

SCKx

bit 0

Shift Control

Edge

Select

F

P

Enable 

Sync

Control

Transfer

Transfer

Write SPIxBUF

Read SPIxBUF

16

SPIxCON1<1:0>

SPIxCON1<4:2>

Master Clock

Note 1: In Standard mode, the FIFO is only one level deep.

Clock

Control

SPIxSR

8-Level FIFO

Transmit Buffer

8-Level FIFO

Receive Buffer

SPIxBUF

Primary

1:1/4/16/64

Prescaler

Secondary

Prescaler

1:1 to 1:8