L99LD21 datasheet(30/73 Pages) STMICROELECTRONICS

30 / 73 page

SPI functional description

L99LD21

30/73

DS11130 Rev 5

Where:

OCx: Operation Code

Ax : Address

Dx: Data bit

Command Byte

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

which specifies the type of operation (<Read>, <Write>, <Read and Clear>, <Read Device

Information>) and a 6 bit address.

The <Write Mode> and <Read Mode> operations allow access to the RAM of the device.

A <Read and Clear Mode> operation is used to read a status register and subsequently

clears its content.

The <Read Device Information> allows access to the ROM area which contains device

related information.

Global Status Byte

According to the ST SPI 4.1 standard, the first byte on the SDO pad during each command

reports the global status of the chip:

Table 8. Data byte 0

Data byte 0

Bit

76543210

Name

Table 9. Operation code definition

OC1

OC0

Meaning

Table 10. Global Status Byte

Global Status Byte

Bit

2928

272625

Name

GSBN

RSTB

SPIE

FE2

FE1

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