Electrical – How do wiegand device really works

cardparityprotocol

As far as my understanding, wiegand device should be connected to wiegand controller so they can communicate in wiegand protocol which is 2 parity bit and the 24 data bit (the Standard wiegand 26).

So let's take an EM4200 card as my example. EM card with 40 bit id. Let's say it's ID is 1234567890(hex) or in binary:
0001 0010 0011 0100 0101 0110 0111 1000 1001 0000

Using a wiegand EM Reader, it transmit 123456, or the 3 byte
0001 0010 0011 0100 0101 0110

This would only equal to 24, so where is the 2 missing parity bit?

Same goes with UHF card. But with HID card, there is really a slot for parity bit on its memory structure.

Someone please share your idea.

Thank you.

Best Answer

* 26-Bit Wiegand Format: 
* Bit 1 = Even Parity over Bits 2 - 13
* Bits 2 - 9 = Facility Code (0 to 255) Bit 2 is MSB
* Bits 10 - 25 = ID Number (0 to 65,535) Bit 10 is MSB
* Bits 26 Odd parity over bits 14 to 25

ref

Parity is not passed thru. Rather error messages on length are sent from reader.

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