WRITE ONCE type registers

Hello all,

If anyone knows how can we design WRITE ONCE type memory elements using VHDL or Verilog which means, "The register can be written only one time during the device lifetime, the value is kept after power cycle or any type of reset", please help.

Thanks and Regards,
Akhil Kumar

if you set an initial value to the register, and that value keeps unchange at all, maybe the optimization step will connect it to VDD or VSS. Or why don't you connect it to VDD　or VSS directly?Register can be saved.

nature0303 said:

if you set an initial value to the register, and that value keeps unchange at all, maybe the optimization step will connect it to VDD or VSS. Or why don't you connect it to VDD　or VSS directly?Register can be saved.

Click to expand...

@nature0303: Your comment will be applicable to the constant value on data line, in that case we can directly connect the data line to Vdd or Vss as per the value but here write while device is in operation is possible. In this case once (Write Once) processor has written this bit, request for re-write will be ignored and the written value will be retained after reset or power down also. Means I want to implement a non-volatile register that can be written once and read many times while the device is in operation.

Thanks

Your apparently talking about programmable ROM cells. It's a matter of specific chip structures, they may be availabe as library elements in an ASIC or FPGA family. There's no specific means to describe them in HDL.

FvM said:

Your apparently talking about programmable ROM cells. It's a matter of specific chip structures, they may be availabe as library elements in an ASIC or FPGA family. There's no specific means to describe them in HDL.

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But I want to implement some information holders in my HDL which are non-volatile. How can I do this?

How about using OTP??? It's guess. Am nt very sure.

Others can correct me if wrong

er.akhilkumar said:

Hello all,

If anyone knows how can we design WRITE ONCE type memory elements using VHDL or Verilog which means, "The register can be written only one time during the device lifetime, the value is kept after power cycle or any type of reset", please help.

Thanks and Regards,
Akhil Kumar

Click to expand...

An one time programable cell is an OTP.
So you need a special component for that or a fuse.
Check the ip provider in the targeted technology.

The issue with a ROM, you need a metal mask specific for the programation (VIA or contact, usually).

Well,you say the written bit will not change even after power-down,that means to be an hard-ware change, only programmable device like EEPROM ，VHDL can't realise this function.

So i really advise you to look back in to your design to look for better ways to realize your design.