3 bit multiplier11/14/2022 In the case of that happening, RLCA actually acts different from SLA A or ADD A,A (in some cases more usable, in some cases less usable). When programming multiplications you must always make sure the result will never exeed 255, in other words a carry may not occur. On a sidenote, instead of using ADD A,A, you can also use RLCA, which effectively behaves the same. So ADD A,A is exactly the same as SLA A, or a multiplication by two. If you use register A you can multiply faster by using the ADD A,A instruction, which is 5 T-states per instruction instead of 8. By doing several shifts in sequence you can very easily multiply by any power of 2. This shifting can be done using the SLA r instruction. When you shift a register 1 bit to the left, you multiply the value of the register with 2. Next, it provides a number of optimized generic multiplication and division routines for various bit-depths, and even a square root routine. First it introduces you to multiplications using shifts, which are very fast and can be used if one of the multiplication parameters is a fixed number. This article presents you with optimized methods for multiplication. The programmer might take a multiplication routine from a book or a magazine, which may not necessarily be optimized for the specific case (or optimized at all), or he might even uses a routine that works by adding the same value n times, which is pretty much the worst solution to the problem. Because the Z80 does not have a built-in multiplication instructions, when a programmer wants to do a multiplication he has to it manually.
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