PL460 datasheet(26/48 Pages) MICROCHIP

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PL460

Serial Peripheral Interface (SPI)

Data Sheet

DS60001666D - 26

Serial Peripheral Interface (SPI)

8.1.

Description

The SPI circuit is a synchronous serial data link that provides communication with external devices

in client mode. The Serial Peripheral Interface is essentially a Shift register that serially transmits

data bits to a host SPI device. During a data transfer, SPI host controls the data flow, while the client

device has data shifted in and out by the host.

The SPI system consists of the following two data lines and two control lines:

• MOSI (host out client in): This data line supplies the output data from the host shifted into the

inputs of the clients.

• MISO (host in client out): This data line supplies the output data from a client to the input of the

host. There may be no more than one client transmitting data during any particular transfer.

• SCK (Serial Clock): This control line is driven by the host and regulates the flow of the data bits.

The host can transmit data at a variety of baud rates; there is one SCK pulse for each bit that is

transmitted.

• CS (Peripheral Chip Select): This control line allows clients to be turned on and off by hardware.

8.2.

Embedded Characteristics

• Client Serial Peripheral Bus Interface

– 8-bit to 16-bit data length

• Client Mode Operates on SCK, Asynchronously with Core and Bus Clock

8.3.

Signal Description

The pins used for interfacing the compliant external devices are multiplexed with PIO lines.

Table 8-1. I/O Lines

Signal

Pin Description

Client

I/O Line

MISO

Host In Client Out

Output

MOSI

Host Out Client In

Input

Peripheral Chip Select/Client Select

Input

SCK

Serial Clock

Input

8.4.

Functional Description

8.4.1.

Data Transfer

Four combinations of polarity and phase are available for data transfers. Consequently, a host/client

pair must use the same parameter pair values to communicate.

The table below shows the four modes and corresponding parameter settings.

Table 8-2. SPI Bus Protocol Modes

SPI Mode

Shift SCK Edge

Capture SCK Edge

SCK Inactive Level

Falling

Rising

Low

Rising

Falling

Low

Rising

Falling

High

Falling

Rising

High

The figures below show examples of data transfers.

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