Digital Components - Decoders And Encoders Flashcards
How could you use a binary decoder to be HIGH when binary 1010 is selected?
The Binary decoder we would use would have an inverter on the LSB and 1st bit after MSB. This way, we can join all values to an AND gate, and the output would be a HIGH. See page 77 for another example
Explain how a 4 bit decoders works
You have 4 inputs that you can control
This means that you have 16 possible combinations
When you selected 0000, the output 0 will go HIGH
When you select 0101, the output 5 will go HIGH etc…
Think of it as a remote that has 4 buttons and you can control 16 different channels.
In a 4 bit decoders, what do the Chip Select lines do?
If either chip select line is off, the outputs will remain LOW so you must have both CS lines ON so that your inputs can make an output HIGH.
If you need more than 16 outputs, you can use the CS lines of the first decoder and connect them to the other decoder.
But remember, you can only work one decoder at a time. So once you have the output of your first decoder, you need to switch both CS lines to LOW, so that the second decoder can be enabled, hence the inverter connecting both CS lines on each decoder on page 78.
Explain how the BCD to Decimal converter works
Same logic as the 4 bit decoders.
- 4 inputs are selected to code for a binary number
- Each binary number such as 1001, will code for its respective output HIGH, in this case 9 will go HIGH
- Often used for digital clocks
How many inputs and outputs does the Decimal to BCD encoder have?
10 inputs
4 outputs
Give a use for the decimal to BCD encoder?
Numeric Keypad
Explain the components of the BCD to 7 segment decoder:
LT
BI
RBO
RBI
Zero suppression
With this decoder, a simple 0001, will tell the 7 segment decoder to turn on the LEDs that display a 1. Super simple!
LT: Lamp Test
When set to HIGH, all of the LEDs are turned on. Usually this is used to make sure all LEDs are working
BI: Blanking input
A master switch, when the Blanking Input is set to LOW, all of the LEDs are off
RBO: Ripple Blanking output
If the Blanking output is set to LOW, and you want all other 7 segment displays to be off as well, set the RBO to HIGH. It effectively carries the BI signal across the whole display
Zero suppression:
When set to HIGH, any unnecessary 0s are hidden
RBI: Ripple Blanking Input
When set to HIGH, and zero suppression is set to HIGH, every other display with unnecessary 0s is hidden
Why does the DEC to BCD converter not have a zero inputs?
It does not need one
