Is this IC active high or active low?

Hi - on page 3 of the datasheet for the Holtek HT12E
(http://holtek.com/pdf/consumer/2_12e.pdf) it says that A0-A7 have a "NMOS
TRANSMISSION GATE PROTECTION DIODE (HT12E)" internal connection. Then it
says "Input pins for address A0~A7 setting. These pins can be externally
set to VSS or left open" So just to clarify - does that mean that when any
of A0-A7 are left open it will be the equivalent of a "1" and when it is
grounded it will be the equivalent of a "0"? So what would happen if I
connected them to VCC? Thanks alot,

Michael

 

You re-enforce the "1".

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| __O Thomas C. Sefranek
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allright - that's what I thought - I just wanted to be sure. I'm putting
one of these in a remote control for my house's outdoor lights. Since I'm
aiming for it to be as small and lightweight as possible - I'm just going
to put holes for jumpers to ground next to pins A0-A7 - that way I can set
the code to whatever I want after I etch the PCB, but I won't have to deal
with the weight and size of a dip switch. For the reciever unit of course
I'll just probabaly use a normal dip switch.

 

I used this chip in a project earlier this year. I just used a DIL switch
to connect A0-A7 to ground (Vss). There is no need for pullups as they
have them internaly. There is therefore no need to connect them to Vcc but
you should be able to drive them directly from a CMOS gate.

Ian