Data Transfer Modes

MC13192 Technical Data, Rev. 3.2

Freescale Semiconductor

5

4

Data Transfer Modes

The MC13192 has two data transfer modes:

1. Packet Mode — Data is buffered in on-chip RAM

2. Streaming Mode — Data is processed word-by-word

The Freescale 802.15.4 MAC software only supports the streaming mode of data transfer. For proprietary

applications, packet mode can be used to conserve MCU resources.

4.1

Packet Structure

Figure 3 shows the packet structure of the MC13192. Payloads of up to 125 bytes are supported. The

MC13192 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 two-byte Frame Check Sequence (FCS) is calculated and

appended to the end of the data.

Figure 3. MC13192 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 back end 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.

If the MC13192 is in packet mode, the data is processed as an entire packet. The MCU is notified that an

entire packet has been received via an interrupt.

If the MC13192 is in streaming mode, the MCU is notified by an interrupt on a word-by-word basis.

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.

Preamble

SFD

FLI

Payload Data

FCS

4 bytes

1 byte

1 byte

125 bytes maximum

2 bytes