Rainbow Electronics W79E8213R - Manual (Page 73)

Preliminary W79E8213/W79E8213R Data Sheet
Publication Release Date: July 11, 2008
- 73 - Revision A2
CPU clocks to pull high then turn off.
The “weak” pull-up is turned on when the input port pin is logic “1” level or itself is logic “1”, and it
provides the most source current for a quasi-bidirectional pin that output is “1” or port latch is logic “0”’.
The “very weak” pull-up is turned on when the port latch is logic “1”. If port latch is logic “0”, it will be
turned off. The very weak pull-up is support a very small current that will pull the pin high if it is left
floating. And the quasi-bidirectional port configuration is shown as below figure.
If port pin is low, it can drives large sink current for output, and it is similar with push-pull and open
drain on sink current output.
Figure 18-1: Quasi-Bidirectional Output
18.2 Open Drain Output Configuration
To configure this mode is turned off all pull-ups. If used similar as a logic output, the port must has an
external pull-up resister. The open drain port configuration is shown as below.
Figure 18-2: Open Drain Output
18.3 Push-Pull Output Configuration