Turbo code encoder COM-7001 -> QPSK modulator COM-1002 -> 
QPSK demodulator COM-1001 -> Turbo code decoder COM-7001 -> BER measurement COM-1005.

Important note: this setup requires that an external 40 MHz clock be provided to the 
COM7001 at the input J2/ pin A1.


Test configuration example: 2 Mbit/s QPSK. 

The turbo-code encoder is placed in signal generator test mode, 
whereby a periodic 2047-bit sequence (PRBS-11) is being transmitted. 
The resulting data stream is FEC encoded, QPSK modulated, QPSK demodulated, FEC decoded. 
The end to end BER is measured using the COM-1005 module. The registers settings are as follows:

COM-7001: 82 22 66 10 CB 00 00 00 00  
COM-1002A: 9A 99 19 00 00 00 FF 00 85 00
COM-1001A: CD CC 0C 00 00 00 80 11
COM-7001: 05 05 00 10 CB 66 00 00 06 
COM-1005: 0D

Proper operation can be verified as follows:

(a) using an oscilloscope probe:

COM-1001 TP1 is high, indicating demodulator carrier lock 

COM-7001 decoder  TP4 shows periodic start of frame pulses every Turbo-code block 
(4096 bits + 32 bit unique word = 2.064ms @ 2 Mbit/s). 

COM-7001 decoder TP2 D_GOUT shows how much decoding capacity is used in the Turbo code 
decoder for this configuration (2 Mbit/s, 0.793 code rate, 6 decoding iterations). 
The duty cycle indicates the available capacity: (2060 - 360)us/2060us = 82.5% capacity available. 

COM-1005 TP1 is high, indicating synchronization with the 2047-bit periodic test pattern 

COM-1005 TP3 is low, showing no bit error pulse.


(b) from the ComBlock control center check the BER (COM-1005 status).
It will show no bit errors (REG 1 through 4) and the synchronization bit (REG5 bit0) is high.
The BER (REG1/2/3/4) should be 0.
The BER synchronization (REG5 bit 0) should be 1.