Panasonic JB-3300 Technical Manual page 315

5. SELF TEST
5.1 Self Test Start Condition
When the system unit holds KBCLK LOW for 40 ms or more, a self test is
requested. After checking that the keyboard is LOW for 1 ms or more, the
system automatically enteres the self-check routine. KBCLK is sampled at
12.5 us intervals to check that it is LOW for 1 ms or more.
Figure 5-1 shows the timing of a self test reguest.
10 ms max Approx. 0.7 Ss
Output Data by
Ordinary Scan
Figure 5-1 Self Test Request
Q) When KBCLK = L continues for 1ms or more after it becomes LOW, the
self test request is accepted.
(2) When KBCLK = L does not continue for 1 ms, the self test request is
not accepted. Six miliseconds later, the keyboard tries again to
output data.
Iv - 15