ka_rai, welcome to the forum!
You are probably not going to find any firmware upgrade for your Matshita UJ-840S laptop drive. Others have tried and failed.
The only firmware I have found is for Sony OEM versions of this drive. These firmwares will only work on Sony OEM drives as far as I know. I'm not sure whether they include bitsetting, but probably not.
You can have a look here.