RFID & reverse Wiegand bits ****

Using RFIdeas Configutility, I read in raw my Hex data as follow: BBBA2164

IF I put a check mark on the "reverse wiegand bits" (not bytes), I will get 26845DDD from which I can extract out 5DDD which is my ID in hex.

What I like to know is What are the Wiegand bits and how did they reverse the bit to go from BBBA2164 to 26845DDD.

Thanks in advance.

All I did was Google it, since I hate to see a post go unanswered.

Weigand encoding is a 26-bit data format used by card reader devices.

http://www.identisource.net/26_bit_format_layout.cfm


You seem to be getting a 32-bit value, not a 26-bit value.

BBBA2164 hex = 1011_1011_1011_1010_0010_0001_0110_0100

26845DDD hex = 0010_0110_1000_0100_0101_1101_1101_1101

So it looks like checking the 'Reverse' box is literally reversing the order of all of the bits in the 32-bit word.

Since you say you can extract your ID value from the reversed order, it seems like the Parity bits are not being included.

I can't tell you much more, except that I suspect that you have an overlap or 'extra' data in the 32-bit element that should be masked out.

Holy Moly! sharp eye you are. Thanks.

Now comes fun part. Swap Byte instruction with Reverse do not work.
I also tried BSR using unload.UL bit as a source bit without success.

The Swap Byte instruction is byte-wise or word-wise. It does not reverse the bits in order.

What exactly do you want to do ?

If you need to get the 26 important bits and ignore the 6 that don't belong, I would use the Masked Move (MVM) instruction.

I want to go from
BBBA2164 hex = 1011_1011_1011_1010_0010_0001_0110_0100
to get
26845DDD hex = 0010_0110_1000_0100_0101_1101_1101_1101

Obviously, I could use 32 separate rungs to reverse it, but I thought someone may have better idea.

I would just brute-force it. Sounds like a great use for an Add-On Instruction, if you're using the A-B Logix 5000 platform.

Yes, sound like an AOI to me too:=). a DINT_REV maybe.

You can reverse all the bits by using the BSL ( SourceBit.0), then immediately follow by BSR (also SourceBit.0). It worked!! Use 32bit Looping Of course.