L99LD02 datasheet(29/66 Pages) STMICROELECTRONICS

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DS12448 Rev 3

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L99LD02

Serial peripheral interface (ST SPI standard)

SPI network. A low signal activates the output driver and a serial communication can

be started. The state during CSN = 0 is called a communication frame.



Serial Data In (SDI)



The input pin is used to transfer data serially into the device. The data applied to SDI

will be sampled on the rising edge of the SCK signal and shifted into an internal 32-bit

shift register. On the rising edge of the CSN signal, the contents of the shift register will

be transferred to the Data Input Register.



Only communication frames with 0 (read GSBN bit), 24 (standard communication

frame), or 24 + (n * 16) (burst read/write) clock pulses are accepted. All others will be

ignored and a communication error will be reported with the next SPI command.



Serial Data Out (SDO)



The data output driver is activated by a logic low level at the CSN input. After a falling

edge of the CSN pin, the SDO pin will leave the tri-state condition and present the

GSBN bit. At all following falling edges of the SCK signal, the following bits of the SPI

frame are shifted out to the SDO pin.



Serial Clock (SCK)



The SCK input is used to synchronize the input and output serial bit streams. The data

input (SDI) is sampled on the rising edge of the SCK and the data output (SDO) will

change with the falling edge of the SCK signal. The SPI can be driven with a SCK

frequency up to 4 MHz.

5.2

Physical layer – protocol

5.2.1

SDI frame

The data-in frame consists of 32 bits (OpCode + Address + Data).

The first two transmitted bits contain the Operation Code which represents the instruction to

be performed. The following 6 bits represent the address on which the operation will be

performed.

The subsequent 24 bits contain the payload data.

Table 9. Command byte (8 bit)

Operating code

Address

Bit

29282726

Name

OC1

OC0

Table 10. Data byte 2

Data byte 2

Bit

2322212019

1716

Name

D23

D22

D21

D20

D19

D18

D17

D16

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