DSP56300FMSLASHAD datasheet(10/64 Pages) FREESCALE

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DSP56374 Data Sheet, Rev. 4.2

Signal Groupings

Freescale Semiconductor

Table 9. Serial Host Interface Signals

Signal

Name

Signal Type

State during

Reset

Signal Description

SCK

Input or output

Tri-stated

SPI Serial Clock—The SCK signal is an output when the SPI is configured

as a master and a Schmitt-trigger input when the SPI is configured as a

slave. When the SPI is configured as a master, the SCK signal is derived

from the internal SHI clock generator. When the SPI is configured as a

slave, the SCK signal is an input, and the clock signal from the external

master synchronizes the data transfer. The SCK signal is ignored by the SPI

if it is defined as a slave and the slave select (SS) signal is not asserted. In

both the master and slave SPI devices, data is shifted on one edge of the

SCK signal and is sampled on the opposite edge where data is stable. Edge

polarity is determined by the SPI transfer protocol.

SCL

Input or output

I2C Serial Clock—SCL carries the clock for I2C bus transactions in the I2C

mode. SCL is a Schmitt-trigger input when configured as a slave and an

open-drain output when configured as a master. SCL should be connected

to VDD through an external pull-up resistor according to the I

specifications.

This signal is tri-stated during hardware, software, and individual reset.

This pin has an internal pull up resistor.

This input is 5 V tolerant.

MISO

Input or output

Tri-stated

SPI Master-In-Slave-Out—When the SPI is configured as a master, MISO

is the master data input line. The MISO signal is used in conjunction with the

MOSI signal for transmitting and receiving serial data. This signal is a

Schmitt-trigger input when configured for the SPI Master mode, an output

when configured for the SPI Slave mode, and tri-stated if configured for the

SPI Slave mode when SS is de-asserted. An external pull-up resistor is not

required for SPI operation.

SDA

Input or

open-drain

output

I2C Data and Acknowledge—In I2C mode, SDA is a Schmitt-trigger input

when receiving and an open-drain output when transmitting. SDA should be

connected to VDD through a pull-up resistor. SDA carries the data for I

transactions. The data in SDA must be stable during the high period of SCL.

The data in SDA is only allowed to change when SCL is low. When the bus

is free, SDA is high. The SDA line is only allowed to change during the time

SCL is high in the case of start and stop events. A high-to-low transition of

the SDA line while SCL is high is a unique situation, and is defined as the

start event. A low-to-high transition of SDA while SCL is high is a unique

situation defined as the stop event.

This signal is tri-stated during hardware, software, and individual reset.

Thus, there is no need for an external pull-up in this state.

This pin has an internal pull up resistor.

This input is 5 V tolerant.

DSP56300FM/AD Datasheet(PDF) 10 Page - Freescale Semiconductor, Inc

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