Panasonic JB-3300 Technical Manual page 309

(2) When KBDATA = L and KBCLK = H at the system unit:
When the system unit sets KBDATA to LOW, the keyboard does not output
data to KBDATA; it stores the data in the buffer (16 bytes) ona
first-in-first-out basis.
Output Routine
Outputs the
first clock
Start bit
' '
KBDATA L
'H!
Outputs the
Stops CLK and
items described
stores data in
in (1)
buffer
Scans, and
attempt output
from the
buffer at 6 ms
intervals
1
Figure 4-6 Output Condition
Iv - 9