L99UDL01 datasheet(44/88 Pages) STMICROELECTRONICS

44 / 88 page

Serial communications

L99UDL01

44/88

DS12511 Rev 5

Figure 14. SPI command protocol description

5.5

Operating codes

The operating code is used to distinguish different modes in the registers of the slave

device.

A Write Operation will lead to a modification of the addressed data by the payload if a write

access is allowed (e.g. Control Register, valid data). Beside this a shift out of the content

(data present at Communication Start) of the registers is performed.

A Read Operation shifts out the data present in the addressed register at Communication

Start. The payload data will be ignored and internal data will not be modified.

A Read & Clear Operation will lead to a clear of addressed status bits. The bits to be cleared

are defined first by address, second by payload bits set to ‘1’. Beside this a shift out of the

content (data present at Communication Start) of the registers is performed.

Note:

Status registers which change status during communication could be cleared by the actual

Read & Clear Operation and are neither reported in actual communication nor in the

following communications. To avoid a loss of any reported status it is recommended to just

clear status registers which are already reported in the previous communication (Selective

Bitwise Clear).

OC1 OC0

D15

D14

D13

D12

D11

D10

OPCODE

ADDRESS

DATA Byte 1

DATA Byte 2

MSB

LSB

time

Table 18. Op code description

OC1

OC0

Description

Write operation

Read operation

Read & clear operation

Read device information

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