ZBasic AN-203
The I/O pins 18-20 are used to select the desired input and pin 17 is used to read the state of the selected input. The reason is because the first line in the GetInput() function reads the value of Register.PortA, modifies it and writes it back.| Part No. | AN-203 |
|---|---|
| Datasheet | AN-203 Download |
| Manufacturer | ZBasic |
| Description | I/O Expansion |
| Buy | Stock & Price |
ZBasic AN-203 I/O Expansion Techniques Introduction Application Note On more complex projects it is often the case that more I/O lines are needed than the number that are available on the chosen processor. In this situation, you might first try to redesign the application to require fewer I/O lines. For example, you may be able to use a given output for multiple purposes. If you still need additional I/O lines, there are several techniques that you might employ, separately or in combination, to solve the problem. Although the examples given in this application note are based on the ZX-24, the principles can be equally well applied to the other ZX processors. Using a Multiplexer for Multiple Inputs If your application has a number of signals that only need to be connected to the processor when it is time to read the input, you may benefit from utilizing an external digital multiplexer. These devices allow 1 of N input signals to be selected for passing on to the processor, where N is a power of two.
