Just looking for some examples of MSI circuits used for doing arithmetic. I understand MSI circuits have more than 10 but less than 100 gates, or less than 500 components.
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asked Mar 20, 2015 at 2:53
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2 Answers
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Probably one of the most widely used MSI arithmetic circuits is the 74283 4-bit adder. Several of them could be wired in series to perform 8-bit, 16 bit or even 32-bit operations.
This is the internal circuitry of a 74HC283 from Philips:
which shows it is clearly of MSI complexity.
Another popular chip was the 74181 bit-slice arithmetic logic unit. It is a step up from a simple 4-bit adder, and could perform all the traditional add / subtract / decrement operations with or without carry, as well as AND / NAND, OR / NOR, XOR, and shift. Like the 74283, it could be ganged together to work with various word lengths.
This chip was used in the core of the CPU of such computers as the PDP-11 and VAX 11/780. Here is its internal structure:
Unlike the 74HC283, I don't believe the 74181 is being made anymore.
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I believe smaller GALs like GAL16V8 and GAL22V10 counts as MSI, and those can certainly be configured into behaving like an ALU. Original GALs are no longer made and sold, but compatible chips from other manufacturers like Atmel are still available.
Actually in my school, old 74F181-based kits are maintained with GAL22V10 programmed to emulate them. L
answered Mar 20, 2015 at 9:57