MC13201 Technical Data, Rev. 1.3,

Freescale Semiconductor

5

4

Data Transfer Mode

The MC13201 has a data transfer mode called Packet Mode where data is buffered in on-chip Packet

RAMs. There is a TX Packet RAM and an RX Packet RAM, each of which are 64 locations by 16 bits

wide.

4.1

Packet Structure

Figure 3 shows the packet structure of the MC13201 which is consistent with the 802.15.4 Standard.

Payloads of up to 125 bytes are supported. The MC13201 adds a four-byte preamble, a one-byte Start of

Frame Delimiter (SFD), and a one-byte Frame Length Indicator (FLI) before the data. A Frame Check

Sequence (FCS) is calculated and appended to the end of the data.

Figure 3. MC13201 Packet Structure

4.2

Receive Path Description

In the receive signal path, the RF input is converted to low IF In-phase and Quadrature (I & Q) signals

through two down-conversion stages. A Clear Channel Assessment (CCA) can be performed based upon

the baseband energy integrated over a specific time interval. The digital backend performs Differential

Chip Detection (DCD), the correlator “de-spreads” the Direct Sequence Spread Spectrum (DSSS) Offset

QPSK (O-QPSK) signal, determines the symbols and packets, and detects the data.

The preamble, SFD, and FLI are parsed and used to detect the payload data and FCS which are stored in

RAM. A two-byte FCS is calculated on the received data and compared to the FCS value appended to the

transmitted data, which generates a Cyclical Redundancy Check (CRC) result. Link Quality is measured

over a 64 µs period after the packet preamble and stored in RAM.

The MC13201 uses a packet mode where the data is processed as an entire packet and stored in Rx Packet

RAM. The MCU is notified that an entire packet has been received via an interrupt.

Figure 4 shows CCA reported power level versus input power. Note that CCA reported power saturates at

about -57 dBm input power which is well above 802.15.4 Standard requirements. Figure 5 shows energy

detection/LQI reported level versus input power.

NOTE

For both graphs, the required 802.15.4 Standard accuracy and range limits

are shown. A 3.5 dBm offset has been programmed into the CCA reporting

level to center the level over temperature in the graphs.

Preamble

SFD

FLI

Payload Data

FCS

4 bytes

1 byte

1 byte

125 bytes maximum

2 bytes