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4511B BCD to 7-segment decoder driver 
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Learn about BCD counters and BCD to 7-segment decoder drivers by building the DOCTRONICS Digital Clock:
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| DOCTRONICS Digital Clock construction kit |
1. Pin connections
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| 4511B pin connections |
The 4511 
is a BCD to 7-segment decoder driver. Its function is to convert the logic states at the
outputs of a BCD, or binary coded decimal, counter like the 4510 into signals
which will drive a 7-segment display. The display shows the decimal numbers 0-9 and is
easily understood.
2. Truth table
The individual segments making up a 7-segment display are identified by letters as follows:
| 7-segment display |
There are two important types of 7-segment LED display. In a common cathode display, the cathodes of all the LEDs are joined together and the individual segments are illuminated by HIGH voltages. In a common anode display, the anodes of all the LEDs are joined together and the individual segments are illuminated by connecting to a LOW voltage.
The 4511 is designed to drive a common cathode display and won't work with a common anode display. You need to check that you are using the right kind of display before you start building.
The 0.56 in. 7-segment display common cathode available from Rapid works well as part of a prototype board circuit.
When the 4511 is set up correctly, the outputs follow this truth table:
BCD inputs |
segment outputs |
display |
|||||||||
D |
C |
B |
A |
a |
b |
c |
d |
e |
f |
g |
|
0 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
 |
0 |
0 |
0 |
1 |
0 |
1 |
1 |
0 |
0 |
0 |
0 |
 |
0 |
0 |
1 |
0 |
1 |
1 |
0 |
1 |
1 |
0 |
1 |
 |
0 |
0 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
0 |
1 |
 |
0 |
1 |
0 |
0 |
0 |
1 |
1 |
0 |
0 |
1 |
1 |
 |
0 |
1 |
0 |
1 |
1 |
0 |
1 |
1 |
0 |
1 |
1 |
 |
0 |
1 |
1 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
1 |
 |
0 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
0 |
0 |
0 |
 |
1 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
 |
1 |
0 |
0 |
1 |
1 |
1 |
1 |
0 |
0 |
1 |
1 |
 |
There is a question about whether the 6's and 9's should have tails. The 4511 produces a display without tails. If other binary values, greater than 1 0 0 1, are connected to the inputs of the 4511, the outputs are all 0's and the display is blank.
3. Basic operation.
In normal operation, the lamp test and ripple blanking inputs are connected HIGH, and the enable (store) input is connected LOW. The circuit diagram shows the 4511 and a 7-segment common cathode display connected to the outputs of a 4510 BCD counter:
 4511 BCD to 7-segment decoder test circuit |
Click to open a PDF version of the drawing which can be printed out.
To build this circuit follow the prototype board layout from the 4510 Beastie Zone web page and then add the 4511 with connections to a third prototype board, as shown below:
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  4511 BCD to 7-segment decoder test circuit. |
Click to open a PDF version of the drawing which can be printed out.
It is good practice with CMOS circuits to insert a decoupling capacitor, 47 µF or 100 µF, across the power supply. (This helps to prevent the transfer of spikes along the power supply rails.)
- Beasties need power supplies! Don't forget to connect pin 16 of the 4511 to +9 V and pin 8 to 0 V.
This is a complex prototype layout. The best way to get it to work is to build it up in stages, checking that each subsystem works before going on to the next.
Check the pin connections for the 4511 as you build the final part of the circuit:
| pin | name |
connections |
| 1 | input B |
from 4510, output B, pin 11 |
| 2 | input C |
from 4510, output C, pin 14 |
| 3 | lamp test input |
connect HIGH |
| 4 | ripple blanking |
connect HIGH |
| 5 | enable/store |
connect LOW |
| 6 | input D |
from 4510, output D, pin 2 |
| 7 | input A |
from 4510, output A, pin 6 |
| 8 | VSS 0 V |
power supply 0 V |
| 9 | segment e |
7-segment common cathode display, e |
| 10 | segment d |
7-segment common cathode display, d |
| 11 | segment c |
7-segment common cathode display, c |
| 12 | segment b |
7-segment common cathode display, b |
| 13 | segment a |
7-segment common cathode display, a |
| 14 | segment g |
7-segment common cathode display, g |
| 15 | segment f |
7-segment common cathode display, f |
| 16 | VDD +V |
power supply +9 V
(range 5-15 V) |
What happens when you press the RESET switch?
What happens when you connect the UP/DOWN input of the 4510, pin 10, LOW instead of HIGH?
4. Other inputs
When the lamp test input, pin 3, is made LOW, all the segment outputs go HIGH regardless of all other input conditions.
With lamp test HIGH, if the ripple blanking input, pin 4, is made LOW, all the segment outputs are forced LOW. This input can be used to blank leading zeros in a multi-digit display.
The enable/store input controls the action of a 4-bit latch inside the 4511. With enable LOW, the outputs of the latch follow the logic states of the BCD inputs and the 7-segment outputs change accordingly. If enable is made HIGH, the logic states present on the BCD inputs are stored. The 7-segment outputs remain unchanged until enable is made LOW once more. This action allows the display to be updated at intervals.
When you need these inputs, you can work out how to use them by investigating the behaviour of the 4511 in a prototype circuit.
5. Links
Excellent
reference book..
5.1 Data sheets
The links below allow you to download documents in Adobe Acrobat ©, PDF, format. In the unlikely event that you don't already have Acrobat Reader, you can download the latest version direct from Adobe:
4511B data sheet (NXP, 1995)
4511B data sheet (ST Microelectronics, 2002)
5.2 DOCTRONICS links
4510 BCD up/down counter
4518 Dual BCD up counter
4060 binary counter/divider
