Jameco-electronics Rabbit 3000 Instrukcja Użytkownika Strona 60

  • Pobierz
  • Dodaj do moich podręczników
  • Drukuj
  • Strona
    / 349
  • Spis treści
  • BOOKMARKI
  • Oceniono. / 5. Na podstawie oceny klientów
Przeglądanie stron 59
Users Manual 51
4.2 Open-Drain Outputs Used for Key Scan
The Parallel Port D outputs can be individually programmed to be open drain. This is use-
ful for scanning a switch matrix, as shown in Figure 4-2. A row is driven low, then the col-
umns are scanned for a low input line, which indicates a key is closed. This is repeated for
each row. The advantage of using open-drain outputs is that if two keys in the same col-
umn are depressed, there will not be a fight between a driver driving the line high and
another driver driving it low.
Figure 4-2. Using Open-Drain Outputs for Key Scan
o.d.
o.d.
+
+
+
+
+
+
+
Przeglądanie stron 59
1 2 ... 55 56 57 58 59 60 61 62 63 64 65 ... 348 349

Komentarze do niniejszej Instrukcji

Brak uwag