M24LR16E-R datasheet(69/143 Pages) STMICROELECTRONICS

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M24LR16E-R

Request format

Doc ID 018932 Rev 8

69/143

Request format

The request consists of:

●

an SOF,

●

flags,

●

a command code,

●

parameters and data,

●

a CRC,

●

an EOF.

19.1

Request flags

In a request, the “flags” field specifies the actions to be performed by the M24LR16E-R and

whether corresponding fields are present or not.

The flags field consists of eight bits. Bit 3 (Inventory_flag) of the request flag defines the

contents of the four MSBs (bits 5 to 8). When bit 3 is reset (0), bits 5 to 8 define the

M24LR16E-R selection criteria. When bit 3 is set (1), bits 5 to 8 define the M24LR16E-R

Inventory parameters.

Table 26.

General request format

Request_flags

Command code

Parameters

Data

CRC

Table 27.

Definition of request flags 1 to 4

Bit No

Flag

Level

Description

Bit 1

Subcarrier_flag(1)

Subcarrier_flag refers to the M24LR16E-R-to-VCD communication.

A single subcarrier frequency is used by the

M24LR16E-R

Two subcarrier are used by the M24LR16E-R

Bit 2

Data_rate_flag(2)

Data_rate_flag refers to the M24LR16E-R-to-VCD communication.

Low data rate is used

High data rate is used

Bit 3

Inventory_flag

The meaning of flags 5 to 8 is described in Table 28

The meaning of flags 5 to 8 is described in Table 29

Bit 4

Protocol_extension_flag(3)

Protocol_extension_flag must be set to 1 for commands: Read Single Block, Read Multiple Block, Fast

Read Multiple Block, Write Single Block, Get Multiple Block Security Status. Command Get System Info

supports two options: a standard response format when Protocol_extension_flag is set to 0, and a rich

response when protocol extension is set to 1.

No Protocol format extension

Protocol format extension

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