Panasonic JB-3300 Technical Manual page 312

Figure 4-10 shows two of 11 microprocessor outputs to the scan driver.
The scan driver changes the output into low-active signals and passes them
to the key matrix. Therefore, the signals are high during scanning.
When there is a depressed key on the line being scanned, the other line
belonging to this key (6) in the circuit diagram) goes low. In Figure
4.10, for example, the space key is pressed while (a) in the circuit
diagram (Section 9) is being scanned.
Scale on the
abscissa: 2 ms/div
aa ET aN CRIN ———
Top: Microprocessor
en P24 output
Bottom: Microprocessor
aE INE Pa a
P25 output
Figure 4-10 Scan Detector
Line 1 |
|
|
Line 2 |
|
|
i
Line 10 |
Line 11 |
Figure 4-11 Scan Driver Output
As Figure 4-11 shows, a low-active signal is output from the scan driver
only to one line on the X-axis of the key matrix at a time, checking the
Y-direction each time.
IV - 12