M24SR04-Y Datasheet, PDF (60/90 Pages) STMicroelectronics – Support of NDEF data structure

I2C device operation
M24SR04-Y M24SR04-G
7.9
I²C frame format
The I²C frame is composed of three fields:
1. SOD field: contains the device select and the PCB. The PCB field is detailed in
Section 5.2.
2. Payload field: contains the command and its parameter, as defined in the I²C command
set.
3. EOD field: contains the two CRC bytes computed on the SOD but excluding the device
select byte field.
Table 69 shows the format of an I²C frame.
I²C frame
Table 69. I²C frame format
SOD
Payload
EOD
0xAC or 0xAD
1 byte
1 to 251 bytes
2 bytes
Device select
0xAC: to send a request to the M24SR04
0xAD: to read a response of the M24SR04
PCB field
I²C command or I²C answer
2 CRC bytes
7.9.1
Example of I²C frame commands
NDEF Tag Application command
This example presents the I²C frame of an NDEF Tag Application Select command. The I²C
frame is detailed in Table 70.
Field
Table 70. I²C host to M24SR04
SOD
Payload
EOD
Value
0xAC
Device select
PCB field
0x00 A4 04 00 07 D2 76 00 00 85 01 01 00
2 CRC bytes
0x02 or 0x03
Command field
35 C0 or DF BE
Before sending a new command, the I²C host can send an I²C frame to read the M24SR04
answer to the NDEF tag Application Select command.
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