2 4.0 mbps fir frame format, 2 4.0 mbps fir frame format -15, Figure 17-3. 4ppm modulation example -15 – Cirrus Logic EP93xx User Manual
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Copyright 2007 Cirrus Logic
IrDA
EP93xx User’s Guide
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Figure 17-3. 4PPM Modulation Example
17.5.1.2 4.0 Mbps FIR Frame Format
When the 4.0 Mbps transmission rate is used, the high-speed serial/parallel (FIR) interface
within the FIR is used along with the 4PPM bit encoding. The high-speed frame format shown
in
, is similar to the SDLC format with several minor modifications: the start/stop
flags and CRC are twice as long and instead of one start flag, a preamble and start flag of
differing length are used.
Figure 17-4. IrDA (4.0 Mbps) Transmission Format
64
symbols
8
symbols
4 DDs
(8 bits)
4 DDs
(8 bits)
8180 DDs max
(2045 bytes)
16 DDs
(32 bits)
8 symbols
Preamble
Start Flag
Address
Control
(optional)
Data CRC-32
Stop
Flag
Start Flag
|0000|1100|0000|1100|0110|0000|0110|0000|
|0000|1100|0000|1100|0000|0110|0000|0110|
Stop Flag
Preamble
|1000|0000|1010|1000|... repeated 16 times
Receive data sample counter frequency = 6x pulse width, each time-slot sampled on third clock.