Data Transfer Modes
MC13192/MC13193 Technical Data, Rev. 3.1
Freescale Semiconductor 5
4 Data Transfer Modes
The MC13192/MC13193 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/MC13193. Payloads of up to 125 bytes are supported.
The MC13192/MC13193 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/MC13193 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/MC13193 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/MC13193 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
