The inactive signal on terminal Q causes {HEAD ~ AND gate} 612 to mask {TAIL ~ the clock signal} and so operation of diagnostic data port 100 is suspended until DSP 110 again writes to SR flip flop 631 
to mask
The inactive signal on terminal Q causes { HEAD ~ AND gate } 612 to mask { TAIL ~ the clock signal } and so operation of diagnostic data port 100 is suspended until DSP 110 again writes to SR flip flop 631
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH