Problem with writing eeprom memory

[Novacicm]

I am trying to write atmel at28c256 on breadboard so I tied all address lines to ground, and all I/O lines also tied to ground. I untie I/O lines for reading, tie 'WE to high, 'CE to low, and 'OE to low for reading. I am reading all ones at I/O ports, no matter what address. So, when I try to write this eeprom I put 'OE high and with 'WE line I touch to ground so that should write stuff to memory but it does not, all I/O ports were connected. I also made small RC circuit with button on WE but that also does not work. Any toughts?

 

[kellys_eye]

Have you read the data sheet for the device? It gives all the details of the parameters needed to read/write from the device.

http://ww1.microchip.com/downloads/en/DeviceDoc/doc0006.pdf

When you've connected and tried to program the device according to the data sheet and still ahve a problem then get back to us.

 

[Novacicm]

Have you read the data sheet for the device? It gives all the details of the parameters needed to read/write from the device.

http://ww1.microchip.com/downloads/en/DeviceDoc/doc0006.pdf

When you've connected and tried to program the device according to the data sheet and still ahve a problem then get back to us.

Yep, I already saw datasheet and tried to write a memory as it says but stil same problem.

 

[kellys_eye]

I untie I/O lines for reading, tie 'WE to high, 'CE to low, and 'OE to low for reading. I am reading all ones at I/O ports, no matter what address.

You will - a standard 'unprogrammed' EPROM is usually set to FF (all locations).

 

[Novacicm]

You will - a standard 'unprogrammed' EPROM is usually set to FF (all locations).

Yeah I know that but also when I try to write memory to some pattern of 8bits I am always getting FF all ones in memory.

 

[kellys_eye]

So, when I try to write this eeprom I put 'OE high and with 'WE line I touch to ground so that should write stuff to memory but it does not, all I/O ports were connected.

If you have tied all address and data lines to zero the programming function (assuming you get the proper 'low' pulse applied) will write whatever you have set on the data lines to the address you have on the data lines.

Assuming all lines are zero then the programming pules should write 00 to address 0000.

Have you got pull-up resistors on address/data lines?
Have you got proper supply line decoupling in place?
Have you got a de-bounced program signal?