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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

6.4SYNCHRONOUS SERIAL INTERFACE (SSI)

The synchronous serial interface (SSI) provides a full-duplex serial port for serial communication with a variety of serial devices including one or more industry-standard codecs, other DSPs, microprocessors, and peripherals which implement the Motorola SPI.

The user can independently define the following characteristics of the SSI: the number of bits per word, the protocol, the clock, and the transmit/receive synchronization.

The user can select among three modes: normal, on-demand, and network. The normal mode is typically used to interface with devices on a regular or periodic basis. The da- ta-driven on-demand mode is intended to be used to communicate with devices on a nonperiodic basis. The network mode provides time slots in addition to a bit clock and frame synchronization pulse.

The SSI functions with a range of 2 to 32 words of I/O per frame in the network mode. This mode is typically used in star or ring time division multiplex networks with other DSP56K processors and/or codecs. The clock can be programmed to be continuous or gated. Since the transmitter and receiver sections of the SSI are independent, they can be programmed to be synchronous (using a common clock) or asynchronous with respect to each other.

The SSI requires up to six pins, depending on its operating mode. The most common minimum configuration is three pins: transmit data (STD), receive data (SRD) and clock (SCK).

The SSI consists of independent transmitter and receiver sections and a common SSI clock generator. Three to six pins are required for operation, depending on the operating mode selected.

The following is a short list of SSI features:

Three-Pin Interface: TXD – Transmit Data RXD – Receive Data SCLK – Serial Clock

A 10 Mbps at 40 MHz (fosc/4) serial interface

Double Buffered

User Programmable

Separate Transmit and Receive Sections

Control and Status Bits

6 - 76 PORT C MOTOROLA

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

• Interface to a Variety of Serial Devices, Including:

Codecs (usually without additional logic) MC145502

MC145503

MC145505

MC145402 (13-bit linear codec)

MC145554 Family of Codecs

MC145532

Serial Peripherals (A/D, D/A)

Most Industry-Standard A/D, D/A

DSP56ADC16 (16-bit linear A/D)

DSP56K to DSP56K Networks

Motorola SPI Peripherals and Processors

Shift Registers

Interface to Time Division Multiplexed Networks without Additional Logic

Six Pins:

STD SSI Transmit Data

SRD SSI Receive Data

SCK SSI Serial Clock

SC0 Serial Control 0 (defined by SSI mode)

SC1 Serial Control 1 (defined by SSI mode)

SC2 Serial Control 2 (defined by SSI mode)

On-chip Programmable Functions Include: Clock – Continuous, Gated, Internal, External

Synchronization Signals – Bit Length and Word Length TX/RX Timing – Synchronous, Asynchronous Operating Modes – Normal, Network, On-Demand Word Length – 8, 12, 16, 24 Bits

Serial Clock and Frame Sync Generator

Four Interrupt Vectors:

Receive

Receive with Exception

Transmit

Transmit with Exception

MOTOROLA PORT C 6 - 77

For More Information On This Product, Go to: www.freescale.com

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