AN2014 datasheet(38/65 Pages) STMICROELECTRONICS

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Software considerations

AN2014

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DocID10701 Rev 10

The Write Page mode is used to write a block of data bytes in a single shot. The Write Page

mode sequence consists of a write instruction with the start address and one or more data

bytes directly followed by the internal execution of the operation (tW).

•

The maximum number of bytes programmed during a Write Page is limited by the page

length of the product.

•

A data block can be programmed starting at any offset inside the page.

•

The address of the first data byte to program is given in the instruction, other data bytes

are programmed in consecutive addresses.

•

If the last location in a page is reached when shifting in the data bytes during a Write

command, the internal address pointer rolls over to the first byte inside the same page.

It is therefore not possible to store data in two different pages with a single Write Page

instruction.

•

If more data bytes than the page length (for instance 32) are shifted in, only the last

received data bytes (last 32 bytes) are programmed in the page (The 33rd data byte

shifted in will replace the 1st data byte shifted in and so on).

To write to the EEPROM, it is recommended to use the Page mode instead of the byte mode

whenever possible. The programming time (tW) is independent of the number of bytes to

program and the Page mode has two main advantages:

It speeds up the application when storing or updating data.

It minimizes the high-voltage programming stress and naturally extends the cycling

endurance.

5.2.2

Data polling

Data polling is a very safe and optimal way of managing the EEPROM Write time (tW). The

aim is to check the EEPROM status before sending the next instruction, so as to prevent

bad master-slave communications.

Data polling is a software loop used to optimize the write wait time and control the correct

operation of the device. Moreover, software which has data polling will be able to adapt to

different devices regardless of the specified write time.

This data polling algorithm must be coupled to a time-out counter to limit the data polling

time and avoid some endless polling. The timeout limit should be higher than the maximum

write time of all devices used (typically 15 ms should be enough).

I2C products

In I2C products, the device does not respond (NoAck) when a programming operation is in

progress. Data polling thus consists in sending a Device Code in a loop mode and tracking

the EEPROM acknowledgement. It is recommended to poll the device with a Write

instruction.

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