ib technology

14

Weigand 26 bit sequence:-

E

(b0 --------- b11) (b12 -------- b23) O

E

( 0

4

6

0

2

2 ) O

1

0000 0100 0110 0000 0010 0010

1

Where E is EVEN parity bit for bit 0 to 11 and O is ODD parity bit for bits 12 to 23

The base data for the Weigand output is the least significant 4-bytes of the EM4102 or

MCRF200/123 tag data. EM4102 or MCRF200/123 Reader mode selection is by means of an

RWD EEPROM parameter. In addition, parameters control whether the base data byte order

is reversed or if parity bits are added before output.

The complete data frame is output whenever the tag is within the RWD’s antenna field and

the tag has been validated. This output is independent of the normal TTL serial interface

which responds to received commands and replies with the data as requested.

The physical Weigand protocol is asynchronously transmitted as 50 µS LOW pulses on the

appropriate DATA low or DATA high pins. These pulses are separated by 2mS periods. The

Weigand sequence is output a single time whenever a valid tag enters the RF field for the first

time. (NO Weigand output if AUX OUTPUT parameter is ZERO/OFF).

Weigand Protocol Timing Diagram

TTL level

5v

0v

5v

0v

DATA High

DATA Low

50 µS pulse

2mS pulse intervals

DATA

1

0

1

0