L99PD08 datasheet(25/41 Pages) STMICROELECTRONICS

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L99PD08

SPI

Doc ID 15872 Rev 3

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6.2.2

Serial data input (SDI)

This input is used to transfer data serially into the device. It receives the data to be written.

Values are latched on the rising edge of Serial Clock (SCK).

6.2.3

Serial data output (SDO)

This output signal is used to transfer data serially out of the device. Data is shifted out on the

falling edge of Serial Clock (SCK).

SDO also reflects the status of the <Global Error Flag> (Bit 7 of the <Global Status

6.2.4

Chip select not (CSN)

When this input signal is High, the communication interface of the device is deselected and

Serial Data Output (SDO) is high impedance. Driving this input Low enables the

communication. The communication must start and stop on a Low level of Serial Clock

(SCK). A CSN timeout is implemented.

6.3

SPI communication flow

6.3.1

General description

The proposed SPI communication is based on a standard SPI interface structure using CSN

(Chip Select Not), SDI (Serial Data In), SDO (Serial Data Out/Error) and SCK (Serial Clock)

signal lines. Each communication frame consists of an instruction byte which is followed by

1 data byte.

The data returned on DO within the same frame always starts with the <Global Status>

Byte. It provides general status information about the device. It is followed by 1 data byte

containing the current of the addressed register (i. e. ‘In-frame-response’).

6.3.2

Command byte

Each communication frame starts with a command byte. It consists of an operating code

which specifies the type of operation (<Read>, <Write>, <Fault Reset>, <Read Device

Information>) and a 6 bit address.

Note:

OCx: Operating Code

Ax: Address

Table 19.

Command byte

MSB

LSB

Op code

Address

OC1

OC0

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