WM72016 – Secure F-RAM with Gen-2 RFID and Serial Port

Rev. 1.4

May 2011

Page 9 of 32

TAG-TO-READER DATA ENCODING

The WM72016 supports both encoding formats defined in the Gen2 standard:



FM0 baseband (FM0)



Miller modulation of a subcarrier (MMS)

Data encoding is performed in the WM72016 as described in the Gen2 standard. A FM0 data symbol is

transmitted with period T which is defined by the tag-to-reader link frequency. The difference between a logic 0

and a logic 1 is defined by an additional mid-bit transition for a logic 0 as shown below in Figure 6. Data

encoding using Miller modulation of a subcarrier (MMS) is further defined by a rate parameter M that defines the

number of link frequency cycles per data bit: 2, 4, or 8, resulting in data encoding defined as MMS2, MMS4, or

MMS8 respectively. MMS data encoding results in a phase inversion of the sub-carrier frequency when one of

the following conditions occurs:



At the mid-bit of a logic 1 data bit, or



At the bit-boundary of two consecutive logic 0s.

The following set of four figures depicts the data bit values “00”, “01”, “10” and “11” for FM0 and MMS data

encoding formats. The same link frequency is shown for all cases, however the MMS parameter M lengthens the

baseband bit period by 2, 4, or 8 as shown in Figure 7, Figure 8, and Figure 9.

0

T

2T

11

10

01

00

Figure 6. FM0 Data Encoding

0

2T

4T

11

10

01

00

Figure 7. MMS2 Data Encoding

11

10

01

00

0

4T

8T

Figure 8. MMS4 Data Encoding

11

10

01

00

0

8T

16T

Figure 9. MMS8 Data Encoding