We used one 74LS47 IC in our lab, which we connected to a 7-segment display and tested the outputs. Now our instructor has told us to cascade two 7447 ICs together and implement it on a 7-segment display. Also, the instructor did not show us how to cascade 2 ICs together in general. So I apologize if my question sounds a bit silly.

This is the assignment question we got:

Design and implement an 8-bit BCD to 7 Segment Display using the concept studied in the lab today. Hint: You will need to connect two 7447 ICs i.e. cascading of two ICs. Draw the circuit below and make its truth table.

  • 1
    \$\begingroup\$ Have you read the datasheet to see what all the pins do? The weird pins whose functionality tends not to make any sense and be useless when using the IC alone are usually the pins meant for cascading. \$\endgroup\$
    – DKNguyen
    May 19, 2022 at 19:24
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    \$\begingroup\$ "Cascade" is a poor choice of wording -- it implies that the output of one 7447 is feeding the input of the other. Beyond that -- what was the concept that you should have learned in the lab that day? There's probably a hint there to what you should be doing. \$\endgroup\$
    – TimWescott
    May 19, 2022 at 19:25
  • \$\begingroup\$ yes i have, pins 1,2 & 6,7 are inputs A0-A3 and the pins from 15-9 need to be connected to a resister and then to the corresponding letter in the 7-segment led. \$\endgroup\$ May 19, 2022 at 19:28
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    \$\begingroup\$ "The TTL Databook" shows examples of cascading ICs where in makes sense (e.g. counters, adders etc) \$\endgroup\$ May 19, 2022 at 19:30
  • \$\begingroup\$ @TimWescott I was thinking the same thing merging the outputs of 1 ic into the other ic. Also, we were only given information on the pin configurations of 7447 ic and the 7-segment-display, other than that I believe nothing conceptual was told in the lab. \$\endgroup\$ May 19, 2022 at 19:37

2 Answers 2


The 74xx47 chip can be configured (with /RBI low) to leave the output blank instead of displaying a zero digit, so that the two-digit output is " 0" instead of "00".

With the "ripple-blank" input and output (/RBO), multiple chips can coordinate so that all leading zero digits are blanked, e.g., "0005" → "   5" but "0105" → " 105".

However, for only two chips, cascading the ripple-blank signal does not really make sense, because the first digit must always be blanked when zero, and the second digit must never be blanked when zero. In other words, the two chips work completely independently, which is not what I would call "cascaded".

If you do cascade the two chips with /RBO/RBI, the result would be that zero would be displayed as completely blank. This might or might not be what the assignment wants you to do.


enter image description hereI found the answer to my question. This image was taken from an article that beautifully explained how to cascade 2 ICs together and provided more helpful information that I needed. Thank you all for trying to help me I really appreciate it. Also, I asked my instructor for more clarity and they haven't even answered my question for 4 days.

Here is the link https://www.electronics-tutorials.ws/counter/7-segment-display.html


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