Standardisation - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 251

4.833 ms

F
2

F
3

F
4

F
5

F
6

F
7

F
8

F
9

F
A

F
B

F
C

F
D

F
E

0123456789AB

9.44 µ s
18.8 s

µ

Figure 9.30 The '1 of 256' coding is generated by the combination of 512 time slots of 9.44 µ s
length. The value of the digit to be transferred in the value range 0-255 can be determined from
the position in time of a modulation pulse. A modulation pulse can only occur at an uneven
time slot (1 , 3 , 5 , 7 ,... )

SOF Byte 1 Byte 2 ... Byte N EOF

Figure 9.31 Structure of a message block (framing) made up of frame start signal (SOF), data
and frame end signal (EOF)

9.44 µ s 9.44 µ s 9.44 µ s 9.44 µ s 9.44 µ s 9.44 µ s 9.44 µ s 9.44 µ s

Figure 9.32 Coding of the SOF signal at the beginning of a data transmission using '1 of
256' coding

for a byte is 75.52 µ s, which corresponds with eight time slots of 9.44 µ s. A modulation
pulse can only be transmitted at an uneven time slot (counting begins at zero). The
value n of a transmitted figure can easily be determined from the pulse position:

Pulse position = ( 2 · n) + 1 ( 9 . 2 )

The data rate resulting from the time taken to transmit a byte (75.52 µ s) is

26.48 Kbit/s.