Holtek HT12E Encoder issue

[technocrate]

I have a fan controller with its remote control and a unit that attaches to the fan. The remote control with 4 buttons runs on 9 V battery.
I opened up the remote control and saw HT-12E AAAFAA marking on the chip. I replaced it with a Holtek HT-12E chip that I had purchased from a vendor.
But now the remote control is not working. Why?

I have spent now about 2 days and can not figure out why this remote does not work but have run out of answers. Please help

The Holtek datasheet for HT-12E says that
A0-A7 lines are input with NMOS Transmission Gate protection diode, what does this means?
In addition, the original circuit shows that A6 and A7 are high but as soon as I replace it, these two pins goes Low?

Thank you in advance.

 

[pranam77]

If its was the same chip before and now is replaced with the similar one, it should work unless the address pins (Pin1 to pin 8) of the HT12e OR The receiver chip HT12D are connected differently or you have some problem with some other section. Verify you get correct voltage (9V or 5V whatever is used) to the chip too.
Cheers

 

[technocrate]

Thank you Pranam77. The chip before is a chinese HT-12E and it was replaced with HOLTEK HT12E, so these chips are identical. I have many of these circuit boards but as soon as HOLTEK chip is inserted it stops working. So the circuit does not have a problem anywhere I suspect the HT12E.

While reading the HT12E datasheet it mentions that A0-A7 and AD8-AD11 pins have NMOS Transmission gate protection diode, I don't know what does this means? Does this means that these pins are pulled high? as shown in the datasheet internal connections diagram?