MCRF202 datasheet(5/20 Pages) MICROCHIP

Teilenummer	MCRF202

Bauteilbeschribung	125 kHz Passive RFID Device with Sensor Input

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 2003 Microchip Technology Inc.

DS21308E-page 5

MCRF202

2.2

Configuration Register and

Control Logic

The configuration register determines the operational

parameters of the device. It directly controls logic

blocks which generate the baud rate, memory size,

encoded data, modulation protocol, etc. CB11 is

always a zero. Once the array is successfully pro-

grammed at the factory, the lock bit CB12 is set. When

the lock bit is set, programming and erasing the device

becomes permanently disabled. Table 2-1 contains a

description of the control register bit functions.

2.2.1

BAUD RATE TIMING OPTION

The chip will access data at a baud rate determined by

bits CB2, CB3, and CB4 of the configuration register.

For example, MOD32 (CB2 = 0, CB3 = 1, CB4 = 1) has

32 RF cycles per bit. This gives the data rate of 4 kHz

for the RF carrier frequency of 128 kHz.

2.2.2

DATA ENCODING OPTION

This logic acts upon the serial data being read from the

EEPROM. The logic encodes the data according to the

configuration bits CB6 and CB7. CB6 and CB7 deter-

mine the data encoding method. The available choices

are:

• Non-return to zero-level (NRZ_L)

• Biphase_S (Differential)

• Biphase_L (Manchester)

• Inverted Manchester

2.2.3

MODULATION OPTION

CB8 and CB9 determine the modulation protocol of the

encoded data. The available choices are:

• ASK

•FSK

• PSK_1

• PSK_2

When ASK (direct) option is chosen, the encoded data

is fed into the modulation transistor without change.

When FSK option is chosen, the encoded data is rep-

resented by:

a)

Sets of 10 RF carrier cycles (first 5 cycles

→

higher amplitude, the last 5 cycles

→ lower

amplitude) for logic “high” level.

b)

Sets of 8 RF carrier cycles (first 4 cycles

→

higher amplitude, the last 4 cycles

→ lower

amplitude) for logic “low” level.

For example, FSK signal for MOD40 is represented:

a)

4 sets of 10 RF carrier cycles for data ‘1’.

b)

5 sets of 8 RF carrier cycles for data ‘0’.

Refer to Figure 2-2 for the FSK signal with MOD40

option.

The PSK_1 represents change in the phase of the

modulation signal at the change of the encoded data.

For example, the phase changes when the encoded

data is changed from ‘1’ to ‘0’, or from ‘0’ to ‘1’.

The PSK_2 represents change in the phase at the

change on ‘1’. For example, the phase changes when

the encoded data is changed from ‘0’ to ‘1’, or from ‘1’

to ‘1’.

FIGURE 2-2:

ENCODED DATA AND FSK OUTPUT SIGNAL FOR MOD40 OPTION

Encoded Data ‘1’

Encoded Data ‘0’

40 RF cycles

5 cycles (HI)

5 cycles (LO)

4 cycles (HI)

4 cycles (LO)

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