M95512 failed to read immediately after writing

[jiafeimao]

I write four bytes of data to M95512, and after the writing is completed, I read these four bytes. I must delay the writing for more than 3 milliseconds to read the correct bytes. Delays less than 3 milliseconds will read 0XFF. Why is this?

What does “Byte Write within 5 ms” mean？Does it take 5ms to write a byte? Looking forward to any suggestions and responses.

[Peter BENSCH · Accepted solution]

Welcome @jiafeimao, to the community!

The various writes can in fact take a maximum of 5ms for a single byte (data sheet, table 19). However, the time can vary, which is why it makes sense to determine the end of the write process with bit WIP (bit 0 of the Read Status Register RDSR, see data sheet, section 6.3.1).

However, a Page Write takes just as long, but can write several bytes in one go from a given start address.

One more addition to the write cycle time tW - the data sheet mentions about this in a note in section 6.6:

The self-timed write cycle tW is internally executed as a sequence of two consecutive events: [Erase addressed byte(s)], followed by [Program addressed byte(s)].

When writing a byte, the byte must first be erased, which is why it can take a little longer for individual bytes. With page write, the bytes are erased in one go, which is why writing is significantly faster.

Does it answer your question?

Regards
/Peter

BTW: you should also take the opportunity to download the new data sheet, your extract is still from the old revision 23.