![Rabbit 3000 Скачать руководство пользователя страница 59](http://html2.mh-extra.com/html/rabbit/3000/3000_user-manual_3114034059.webp)
User’s 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.
+
+
+
+
+
+
+
Содержание 3000
Страница 1: ...Rabbit 3000 Microprocessor User s Manual 019 0108 020426 A...
Страница 8: ...Rabbit 3000 Microprocessor...
Страница 28: ...20 Rabbit 3000 Microprocessor...
Страница 73: ...User s Manual 65 6 RABBIT INTERNAL I O REGISTERS...
Страница 122: ...114 Rabbit 3000 Microprocessor...
Страница 138: ...130 Rabbit 3000 Microprocessor...
Страница 150: ...142 Rabbit 3000 Microprocessor...
Страница 188: ...180 Rabbit 3000 Microprocessor...
Страница 208: ...200 Rabbit 3000 Microprocessor...
Страница 228: ...220 Rabbit 3000 Microprocessor...
Страница 232: ...224 Rabbit 3000 Microprocessor...
Страница 238: ...230 Rabbit 3000 Microprocessor...
Страница 260: ...252 Rabbit 3000 Microprocessor...
Страница 266: ......