EEPROM Read/Write

TucsonDon

Member

• Jul 23, 2018

• #1

I am using MPLab and MCC on a PIC18F45K22. My question is if I write a float to the eeprom will the address counter increment itself for the four bytes or will I need to use a for loop and advance the address counter?

 

dknguyen

Well-Known Member

Most Helpful Member

• Jul 23, 2018

• #2

The datasheet doesn't say?

I wish my ARM had an EEPROM. I'm scared of simulating EEPROM using the flash because that's where the program also is lol

 

TucsonDon

Member

• Jul 23, 2018

• #3

I didn't see anything in the data sheet

 

dknguyen

Well-Known Member

Most Helpful Member

• Jul 23, 2018

• #4

Well, you could test just by writing something, and reading the address register to see if it's the same as what it was before and lighting up an LED if it is.

I would think it doesn't auto-increment though since I also did not see it anywhere in the datasheet where I would have expected to see it.

 

dknguyen

Well-Known Member

Most Helpful Member

• Jul 23, 2018

• #5

Ignore this post.

 

Attachments

• EEPROM.PNG

  83.2 KB · Views: 290

Last edited: Jul 23, 2018

Nigel Goodwin

Super Moderator

Most Helpful Member

• Jul 23, 2018

• #6

It's just you

There's only a single write there, the 0x55 and 0xAA are simply to make the write happen.

 

dknguyen

Well-Known Member

Most Helpful Member

• Jul 23, 2018

• #7

Nigel Goodwin said:

It's just you

There's only a single write there, the 0x55 and 0xAA are simply to make the write happen.

Click to expand...

Yeah I just noticed that was a unlocking sequence. I thought it was weird they overwrote the same thing to the register and then set the WR bit.

 

Ian Rogers

User Extraordinaire

Forum Supporter

Most Helpful Member

• Jul 24, 2018

• #8

To answer you question !!

To store a float is easier if you serialise it... A float is 4 bytes so

union{

float x;
unsigned char serialise[4];​

} storefloat;

// writing
for(x = 0;x<4;x++){

writeeeprom(x, storefloat.serialise[x];
eepromwritedelay();​

}

// reading
for(x = 0;x<4;x++){

storefloat.serialise[x] = readeeprom(x );​

}

 

Ian Rogers

User Extraordinaire

Forum Supporter

Most Helpful Member

• Jul 24, 2018

• #9

Sorry! I misread the OP... I see what you mean... You want to write all the bytes in one go..

Normally serial eeproms have a "Housekeeping" which means if the eeprom supports page writes an entire page may be written to a scratchpad ( sram) and transferred internally... I do not think the inbuilt EEprom supports page writes on a PIC... So single write may be the only option..