PIC12F1840 + I2C 24FC1025 EEPROM

The 24FC1025 is a serial I2C EEPROM memory fabricated by microchip, it has 1024Kbits (128KB) of memory space and it is divided in two parts each one of 512Kbits (64KB); the first part goes from address 0x0000 to 0xFFFF and the second part goes from 0x10000 to 0x1FFFF.


  • 128KB of memory space
  • 2-Wire serial interface (I2C)
  • Compatibility with 100 KHz, 400 KHz and 1.0 MHz clocks
  • 2 hardware address bits allowing up to 4 devices on bus
  • Hardware Write-Protect
  • 128-Byte page write buffer (3ms typical)
  • Operating voltage: 1.8V – 5.5VPIC12F1840  I2C 24FC1025 EEPROM

Pinout PDIP:

Pin function table:

The control byte is composed by the static address (1010 = 0xA) plus the Bank select bit (It is 16th most significant address bit) plus the physical address on A1 and A0 pins (A2 pin cannot be used and it MUST be connected to VCC) and in the end the R/W bit as you can see in the image below:

The I2C sequences to read or write a byte or page from this device are:

After sending a write command for a byte or a page the memory will start the writing cycle, while it is still busy we must not send another command. To know if the memory is busy or not you must send the same control command used for write and check the acknowledge bit, if acknowledge is received memory is not busy, otherwise it is still busy writing the data.

The below flow chart shows what was previously described above:

At this point you can see it is easy to read and write data to this memory so we will follow with an example.PIC12F1840  I2C 24FC1025 EEPROM schematic

The example consist on generating the values to rotate a led from bit 0 to 7 and backwards (0x01,0x02,0x04,0x08,0x08,0x04,0x02,0x01) and store these values into the first 8 Bytes of the memory (0x00000:0x00007).

Then generate values backwards to the first sequence (0x08,0x04,0x02,0x01,0x01,0x02,0x04,0x08) and save them in the first 8 Bytes of the second half of the memory (0x10000:0x10007).

Next we are going to read each byte of the sequence and show it on a two 8b ports respectively, in the end we must see that one port is a mirror of the other. To do this I use the MCP23017 I/O Expander showing the first sequence on IOA and the other one in IOB.



For more detail: PIC12F1840 + I2C 24FC1025 EEPROM

About The Author

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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