Discussion in "8051 Discussion Forum" started by    Abhinav    Jun 13, 2010.
Sun Jun 13 2010, 06:43 PM
#1
Hi friends

i am a little confused while using AT24C04. like how many addresses are available for storing the data bytes?

The slave address is 1010 for all EEPROM'S so can we use 2 EEPROM's with one micro?

How to store values bigger that a byte in EEPROM?

i am using BASCOM for coding.

thank you all.
Sun Jun 13 2010, 07:57 PM
#2
>The slave address is 1010 for all EEPROM'S so can we use 2 EEPROM's with one micro?
those are upper 4 bits of 7-bit address. the lower 3 bits are configurable which means yes you can use more than 1 rather total of 8 such EEPROMs at a time.

>How to store values bigger that a byte in EEPROM?
split them in 2 or 3 depending on how big your data is..
let say if its a 16-bit value then:
EEPROMWrite(Add, data>>8); // write first 8bits
EEPROMWrite(Add+1, data);//write next 8 bits to next address

sorry i am not good at bascom

and for your doubt regarding the subaddress/data address of EEPROM:
before you calculate the size of sub address you need to know how much memory is addressable. lets take an example of 24C02 EEPROM.
24C02 is 2kbit = 2/8 kByte = 1/4Kb = 256bytes

so to accomodate 256 addresses you need 1 byte (00 to 255). so your sub address will only be of 1 byte.

now lets take case with 24C16
24C16 is 16Kbit = 16/8Kbyte = 2Kb = 2048 bytes
so we need atleast 2 bytes to accomodate 2048 addresses. so sub address now will be of 2 bytes in this case.

so you can see how we decide the internal data addresses of EEPROM.
Tags I2C eeprom addressingEEPROM interfacing 8051I2C EEPROM internal addressingi2c eeprom sub addressHow i2c eeprom addressing works
Mon Jun 14 2010, 07:56 AM
#3
Hi ajay

Thanks for a amazing detailed reply.

As per this website http://www.digchip.com/datasheets/parts/datasheet/054/AT24C04-10PC-1_8.php
we can connect maximum of-

AT24C01/02 = 8
AT24C04 = 4
AT24C08 = 2
AT24C16 = 1

because of their reducing hard wired addressing pins.

I cannot understand fully the meaning of below-

"AT24C04, 4K SERIAL EEPROM: Internally organized with 32 pages of 16 bytes each,
the 4K requires a 9-bit data word address for random word addressing"
as written in datasheet.

"The 4K is internally organized with 256 pages of 2-bytes each."
as described on digichip website.

thank you so much.

Mon Jun 14 2010, 02:25 PM
#4
when addressing register there are two path, first on which page that register lies second what is the address of that register on that particular page.

you can assume MSB of address to be as page address and LSB as address of register on that page. so you can understand better what is page address and how it relates to register address.

even in 8051 we have page addressing of ram in which RAM is organized as 256 pages of 256 bytes each. so total accessible ram by 8051 is 256*256 = 65536 bytes. when interfacing external ram the page address is given by P2 and register address is given by P0. relate to it and you will understand.
Thu Jun 17 2010, 07:07 PM
#5
hi ajay,

now i understood almost all things just one to ask that if start sending data bytes from address 0 then i think i have to send address(16) again after 16 bytes else first byte will be overwritten.

am i right ?


thanks
Thu Jun 17 2010, 07:20 PM
#6
write operation will not work if you dont send a stop after page size limit of EEPROM.

You can see every EEPROM datasheet explains Page write operation differently from byte write operation. datasheet will provide you complete details.

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Wed Jul 01 2015, 05:14 PM
ShubhamBansal1996
i am making a project of connecting 4 8051's using a can bus for which i am using mcp2515 and mcp2551.but before making it i want to ensure it works by simulating it on proteus though the two ic's mentioned above dont seem to have models in proteus so is there anyone who can help me with that
ExperimenterUK
Tue Jun 30 2015, 05:24 PM
@sachinmm The 8051 timer can't do 1 second. It can do 50ms so count 20 times
sachinmm
Sat Jun 27 2015, 05:01 AM
how calculate 1 second delay in 8051 by using timer and what value should be store in TH0 & TLO register??
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Fri Jun 26 2015, 08:25 AM
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ExperimenterUK
Wed Jun 17 2015, 01:37 AM
@baz..try adding a hash and a semi colon
Sun Jun 14 2015, 06:31 AM
baz
@ExperimenterUK no..i dont do that i just type message example.. Hello my name is baz and then i click send message,
ExperimenterUK
Sun Jun 14 2015, 01:55 AM
@baz..did you end your message with a hash and a semi colon
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@ExperimenterUK okay thank you...but now I already complete and my dot matrix already light up but when i send message from pc to my hardware project it doesnt show any message on my dot matrix..its only blinking when i click send message....I really dont know whats the problem...I had follow all the steps...schematic and use the coding that have been provided..is it because firstly i had wrong burn the coding in AT24C16?? Is that effect ????

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