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# Remote control design problem with HT6221

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#### p55xp

##### Member
I am designing a ir-remote handset with 8 control keys for my own purpose.
It is working with default address.
Now I face a problem as I tried to use my CUSTOM ADDRESS.
The chip contains a mask rom, according to datasheet (attached) "The current value of ROM1 and ROM2 are both 00H"
My question is : how can I programm the mask rom in the HT6221? or, is it not programmable and the address can only be varied using diodes and resistors as shown in the datasheet application circuit?

#### Attachments

• HT6221.pdf
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#### p55xp

##### Member
With high hope i am waiting for your suggestion, comment and/or judgement on the datasheet highlighted portion on page 5.

#### marcbarker

##### New Member
I clicked the pdf file, but it wouldn't open for me

You can't alter a mask rom program easily. They call it mask rom because it's programmed into the mask used to make the chip.

#### marcbarker

##### New Member
Holtek Taiwan often mention Mask ROM options in their datasheets, I believe that was the source of the confusion you had. It's a nice thought the chip is OTP, but alas, no! Entirely differernt technology!

The information about Mask Rom layer appearing in the datasheet isn't meant for the EndUser. For instance when Holtek make a new production run of Melody Generator ICs, the Client can specify a custom melody of his own to be programmed into the Mask Layer used during chip fabrication.

It would be interesting to learn how much it would cost to customise a run of HT6221s.

#### p55xp

##### Member
Thank you again, for applying your insight and thinking.
You are right, datasheet is the source of misconception and confusion in me.
Alas, my thought is wrong. But think if the address is that easily customisable (as I thought it was) the chip would have been more user friendly.
The chip could have gain good market too.

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