DSSS modulator COM-1012 -> DSSS demodulator COM-1011 -> BER measurement COM-1005.  
Test configuration example: 9.99 Mchip/s,  768 Kbps, Barker code 13, no frequency error, 
noiseless. 

Back to back direct-sequence spread-spectrum modem operations can be verified digitally 
at baseband. The DSSS modulator is configured in signal generator test mode whereby a 
periodic PRBS-11 (2047-bit) sequence is being transmitted. The end to end BER is measured 
using the COM-1005 module. The registers settings are as follows:

COM-1012: 9D EF 3F 0D 00 00 03 00 00 00 00 00 00 00 00 00 FF 00 90 0C
COM-1011: 9D EF 3F 0D 00 00 03 00 00 00 00 00 00 00 00 00 80 00
COM-1005: 0C

Proper operation can be verified as follows:

(a) using an oscilloscope probe:

COM-1011 TP1 is high, indicating demodulator carrier lock 

COM-1011 TP2 is high, indicating demodulator code lock 

COM-1012 TP2 shows the transmitted bit clock. Compare with COM-1011 TP4 (received bit clock). Switch power off/on to force reacquisition. During the short code acquisition, the two clocks move with respect to each other. After code acquisition, the delay between transmit and receive bit clock should settle at the same fixed value. 

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. Depending on the demodulated phase ambiguity, the BER can be either 0 
(no inverted bit) or 0x0F4240 (all bits inverted).