FMT1000 Datasheet, PDF(12/29 Page) Fairchild Semiconductor – Motion Tracking Module with Output of Orientation, Inertial Motion Data and Magnetic Field

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FMT1000 Datasheet, PDF (12/29 Pages) Fairchild Semiconductor – Motion Tracking Module with Output of Orientation, Inertial Motion Data and Magnetic Field

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The following diagram shows a read message transfer using a full write transfer for the opcode followed by a read

transfer to get the data:

Figure 8. Full Write Transfer and Full Read Transfer (I2C)

1.7.5 SPI

The FMT1000-series supports the SPI transport layer.

The FMT1000-series module acts as an SPI Slave. The

Master is defined as the user of the FMT1000-series

module.

SPI Configuration

The FMT1000-series supports 4-wire mode SPI. The

four lines used are:

ï§ Chipselect (SPI_nCS)

ï§ Serial Clock (SPI_SCK)

ï§ Master data in, slave data out (SPI_MISO)

ï§ Master data out, slave data in (SPI_MOSI)

The module uses SPI mode 3; Data is captured on the

rising clock edge and data is latched/propagated on the

falling clock edge. (CPOL=1 and CPHA=1);

Data is clocked-out MSB first. The module uses an 8-bit

data format

Data Transfer

There is a single type of SPI transfer used for all

communications. The diagram below shows the basic

transfer.

Figure 9. SPI Basic Transfer

A transfer is started selecting the Slave by pulling the

SPI_nCS low. The SPI_nCS line is to be kept low for the

duration of the transfer. The Slave will interpret the

rising edge of the SPI_nCS line as the end of the

transfer.

The Master places the data it needs to transmit on the

SPI_MOSI line. The Slave will place its data on the

SPI_MISO line.

The first byte transmitted by the Master is the opcode

which identifies what kind of data is transmitted by the

Master and what kind of data the Master wants to read

from the Slave (See MTSSP).

The second- to fourth byte transmitted are the fill words.

These fill words are needed to give the Slave some time

to prepare the remainder of the transfer. In principal, the

Slave is free to choose the value of the fill word; and its

value should therefore be ignored by the Master.

However, the first 4 bytes transmitted by the FMT1000-

series module are always 0xFA, 0xFF, 0xFF, 0xFF.

Following the first four words are the actual data of the

transfer. It is the responsibility of the Master to

determine how many bytes need to be transferred. The

Master should use the PipeStatus (0x04) opcode of the

MTSSP protocol for this.

Timing

The following timing constraints apply to the SPI transport layer.

FMT1000-series â¢ Rev. 1.0

Figure 10. SPI Timing

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