The 74LS181 at its core is a 4-bit adder, with look-ahead carry. They added some gates, to make it support some additional functions, but I would'nt rate this very useful. The realy nice thing, that is underrated, is the look-ahead-carry, that significantly reduces logic propagation time, that otherwise would occur in adder logic. The full advantage of this solution becomes more noticable, when multiple of these chips are cascaded to form an N-bit adder (8bit, 16bit etc.). The look ahead carry logic greatly reduces logic propagation time in these cases. Without this, it would hardly be possible to compute a 16 bit addition in one CPU cycle. This is, why you want to use the 74LS151, instead of a series of full-adders. Perhaps also look into the sibling chip 74LS182, which handles the look-ahead-carry logic for multiple cascaded 74LS181's. One example with both chips 74LS181 and 74LS182 is given in the datasheet of the 181.
Hi, thank you for your explanation! I've recently recorded a video of the 74LS181 in Italian and hopefully I will publish it in the coming weeks! May I suggest that you use a microphone to improve audio quality? Edit: "recently"
dec means decrement (A - 1). shl is "shift left" as in all the bits are shifted to the left by one position and a zero is filled in. so if you had: 1001 and shifted it left you would have: (1)0010. (the 1 would then go to the carry out so you could chain them together to work with larger numbers) this is useful because shifting a binary number to the left by 1 is basically multiplying it by 2. in fact the way this shift is preformed in the chip is by adding A to itself.
This is super neat. I love this format of video
Bro, you deserve to be subscribed! Thank you for explanation
Hello bro, did you manage to get it work?
I've been fascinated by how CPUs are made. thank you for this interesting video
Thanks for the great walk-through; helped re-inforce my learning.
WHAT IS THE NAME OF COMPONENTS ON THE CIRCUIT?
You really helped me to learn the function of a simple ALU with perfect demonstration. Thanks man.
The 74LS181 at its core is a 4-bit adder, with look-ahead carry. They added some gates, to make it support some additional functions, but I would'nt rate this very useful. The realy nice thing, that is underrated, is the look-ahead-carry, that significantly reduces logic propagation time, that otherwise would occur in adder logic. The full advantage of this solution becomes more noticable, when multiple of these chips are cascaded to form an N-bit adder (8bit, 16bit etc.). The look ahead carry logic greatly reduces logic propagation time in these cases. Without this, it would hardly be possible to compute a 16 bit addition in one CPU cycle. This is, why you want to use the 74LS151, instead of a series of full-adders. Perhaps also look into the sibling chip 74LS182, which handles the look-ahead-carry logic for multiple cascaded 74LS181's. One example with both chips 74LS181 and 74LS182 is given in the datasheet of the 181.
Thank you! It helped me to understand how does it work after dozen incomprehensible papers I looked into. Cheers!
Nice work
wonderful and easy to understand
Hi, thank you for your explanation! I've recently recorded a video of the 74LS181 in Italian and hopefully I will publish it in the coming weeks!
May I suggest that you use a microphone to improve audio quality?
Edit: "recently"
can you give the circuit diagram of the sircuit you use?
How can we design an 8-bit ALU using two 74LS181s?
I'm sorry, I'm new to electronics. How do I work with the table on the right side? With the Active High I/o?
what does the dec a and shl a mean on the improved datasheet?
dec means decrement (A - 1). shl is "shift left" as in all the bits are shifted to the left by one position and a zero is filled in. so if you had: 1001 and shifted it left you would have: (1)0010. (the 1 would then go to the carry out so you could chain them together to work with larger numbers) this is useful because shifting a binary number to the left by 1 is basically multiplying it by 2. in fact the way this shift is preformed in the chip is by adding A to itself.
@@Mekelaina hello, may I ask something?
I assume this was used in the PDP11/?? mini's?