Книга: Introduction to Microprocessors and Microcontrollers

Using just two digits

Using just two digits

If we reduce the number of digits then a wider voltage range can be used for each value and the errors due to noise are likely to occur less often.

We have chosen to use only two digits, 0 and 1, to provide the maximum degree of reliability. A further improvement is to provide a safety zone between each voltage. Instead of taking our supply voltage of 3.3 V and simply using the lower half to represent the digit 0 and the top half for 1, we allocate only the lower third to 0 and the upper third to 1 as shown in Figure 2.9. This means that the noise level will have to be at least 1.1 V (one-third of 3.3 V) to push a level 0 digit up to the minimum value for a level 1.

Figure 2.9 A better choice of voltages

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