The Wiegand interface is a wiring standard used for interconnecting peripherals like fingerprint readers, card swipers or iris recognition devices to controller, Door Panels etc. The Wiegand interface is considered a de facto wiring standard for card swipe mechanisms, especially for electronic data entry.
Wiegand is:
- A specific reader-to-card interface
- A specific binary reader-to-controller interface
- An electronic signal carrying data
- The standard 26-bit binary card data format
- An electromagnetic effect
- A card technology
The Wiegand interface consists of three wires in the physical layer, the first wire is for ground and other two for data transmission, known as Data low/DATA0 and Data high/DATA1.
- No Data : DATA0 and DATA1 are pulled up to high voltage
- “0" : DATA0 wire is pulled to a low voltage while the DATA1 stays at high voltage.
- “1" : DATA0 stays at high voltage, whereas the DATA1 is pulled to a low voltage.
Wiegand Signal
A Pulse Width time between 20 uS and 100 uS, and A Pulse Interval time between 200 uS and 20 mS.
Wiegand Protocol
The communications protocol used on a Wiegand interface is known as the Wiegand protocol. Wiegand is one way communication protocol. The original Wiegand format had one parity bit, 8 bits of facility code, 16 bits of ID code, and a trailing parity bit for a total of 26 bits. The Standard 26-bit Format is an open format. It is a widely used industry standard, and is available from many sources. Almost all access control systems accept the Standard 26-bit Format. There are 255 possible facility codes. There can be up to 65,535 card ID numbers per facility code. The total number of cards that can use the entire range without duplication is 16,711,425.
LPB(Leading Parity Bit) : Even Parity bit of linked to the first 12 data bits.
Facility Code : Programmable field which store user extra information. If not all zero. (Bit 2 is Most Significant Bit)
Credential Data : Different credential data of each user. (Bit 10 is Most Significant Bit)
TPB(Trailing Parity Bit): Odd Parity bit of linked to the last 12 data bits.
Advantages of Wiegand
- Wiegand is easy to implement and use when sending data between two units
- When no encryption is needed or low-level of security is applied, Wiegand has the advantage of being a simple interface
Disadvantages of Wiegand
- If the data sent from the card reader is not encrypted, for example sent in plain text, the information is easily reachable for anyone that listens
- As this protocol is one way, card write data functionality can’t be done using this interface.
