ST72344S2 datasheet(172/247 Pages) STMICROELECTRONICS

172 / 247 page

On-chip peripherals

ST72344xx, ST2345xx

172/247

Doc ID 12321 Rev 6

Figure 74.

16-bit word read operation flowchart

Application note

Taking full advantage of its higher interrupt priority Slave 3 can be used to allow the

addressing master to send data bytes as commands to the ST7. These commands can be

decoded by the ST7 software to perform various operations such as programming the Data

E2PROM via IAP (In-Application Programming).

Slave 3 writes the command byte and other data in the RAM and generates an interrupt.

The ST7 then decodes the command and processes the data as decoded from the

command byte. The ST7 also writes a status byte in the RAM which the addressing master

can poll.

11.7.5

Address handling

As soon as a start condition is detected, the address is received from the SDA line and sent

to the shift register. Then it is compared with the three addresses of the interface to decode

which slave of the interface is being addressed.

Address not matched: the interface ignores it and waits for another Start condition.

Sends address

and read bit

Decodes I2C3SNS address

Decodes R/W bit

Sets read flag

Sends read address

Receives byte 1

Stop condition

Updates current address-

Issues DMA request

Reads 1 word from RAM

Releases DMA

Resets read flag

Halts execution

Resumes execution

Services I2C3SNS interrupt

Reads I2C3SNS status register

Shadow reg => Shift reg

Receives byte 2

Delays while CPU

completes word write

Updates status + DMA CNTL

Word mode?

STOP?

Byte 1 => Shift reg

Byte 2 => Shadow reg

Host

ST7 CPU

ST7 I2C3SNS

Repeat

RAM start address depends on slave address

Byte-Pair Coherency ensured by setting Word Mode + DMA on Words

Normal execution

max

3 cycles

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