Data Format; Specialized Rs-232; Wiegand 26 - EverFocus ERK-871 Instruction Manual

C H A P T E R 3 D A T A F O R M A T
Chapter
3

Data Format

This chapter will briefly introduce the format of reader's output.
Two formats can be used to transfer data from the readers to controllers: specialized
RS-232 and wiegand 26. Specialized RS-232, specially designed for EverAccess system,
is recommended for use to achieve the best performance.

Specialized RS-232

The data speed of specialized RS-232 is 9600 bps. All data including card information
and keypad input has been combined together into a data packet. The data packet is
transferred as ASCII character codes.
The length of one data packet is 22 bytes totally, which contains 1-byte packet header,
1-byte synchronization information, 16-byte card information, 1-byte keypad input, 1-
byte tail (0x30) and 2-byte checksum. The last 2 bytes are the arithmetic checksum of
the previous 20 bytes data.
Each new data packet will be transferred repeatedly for 50 times. After that, a single
idle packet will be transmitted until some new data enters the system. The format of
the idle packet is similar to the normal data packet except that card information bytes
and keypad input bytes will be changed into 0x30, the same as the 1 byte packet tail.
1 2 3~18 19 20 21~22
Keypad Check-
Head SYNC Card information Tail
input sum
Figure 3.1 Specialized RS-232 packet format (byte)

Wiegand 26

As the name implies, each wiegand 26 packet contains 26 bit inside: 2 parity bits and
st
24-bit data. Please refer to Fig 3.2 for details. The 1 bit is the even parity of sequential
th
12 bits and the last bit (the 26 bit) is the odd parity of the 12-bit data before it
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