Synchronous Serial Port Controller

8

This chapter describes the Synchronous Serial Port Controller’s (SSPC) signal definitions and operation for the PXA255 processor usage.

8.1Overview

The SSPC is a full-duplex synchronous serial interface and can connect to a variety of external analog-to-digital (A/D) converters, audio and telecom codecs, and other devices that use serial protocols for transferring data. The SSPC supports National’s Microwire* , Texas Instruments’ Synchronous Serial Protocol* (SSP), and Motorola’s Serial Peripheral Interface* (SPI) protocol.

The SSPC operates in master mode (the attached peripheral functions as a slave) and supports serial bit rates from 7.2 KHz to 1.84 MHz. Serial data formats may range from 4 to 16 bits in length. The SSPC provides 16 entries deep x 16 bits wide transmit and receive data FIFOs.

The FIFOs may be loaded or emptied by the Central Processor Unit (CPU) using programmed I/O, or DMA burst transfers of 4 or 8 half-words per transfer while receiving or transmitting.

8.2Signal Description

This section describes the SSPC signals.

8.2.1External Interface to Synchronous Serial Peripherals

Table 8-1lists the external signals that connect the SSP to an external peripheral.

Table 8-1. External Interface to Codec

Name

Direction

Description

 

 

 

SSPSCLK

Output

Serial bit-rate clock

 

 

 

SSPSFRM

Output

Frame indicator

 

 

 

SSPTXD

Output

Transmit Data (serial data out)

 

 

 

SSPRXD

Input

Receive Data (serial data in)

 

 

 

SSPEXTCLK

Input

External clock which can be selected to drive the serial clock

(SSPSCLK)

 

 

 

 

 

SSPSCLK is the bit-rate clock driven from the SSPC to the peripheral. SSPSCLK is toggled only when data is actively being transmitted and received.

SSPSFRM is the framing signal, indicating the beginning and the end of a serialized data word.

SSPTXD and SSPRXD are the Transmit and Receive serial data lines.

Intel® PXA255 Processor Developer’s Manual

8-1

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Intel PXA255 manual Signal Description, External Interface to Synchronous Serial Peripherals, External Interface to Codec