To get that SSD going, try this (in order): By separating the components out like this, you'll find it easier to 1) write them, 2) maintain them, 3) know what is working and what isn't, design work is one of those things that is done a little bit at a time if you wish to be successful. Another module should have your counter in it, and should actually drive the various pins of the SSD. Use another module to convert this into a list of LED's that need to be turned on. Use one module to convert from a 7-bit binary value to an 8-bit BCD value. This will help you reason about what is going on and produce better quality code. is it properly being set? I can't tell, since it's not a part of your project.įurther, it looks like your are struggling to put too much logic into one component. the only problem you have is how to convert from binary to BCD, right? Something like: which board do you have? Were you able to create all 8-bits of the input using your buttons and switches? Could you display every number that the display can produce? If you can display a pair of hex digits without a problem, then. In your case, you have an 8-bit input, so your synthesis tool should be able to generate a divide in just 4-LUTs and an 8-mux per bit. there's a reason why that example used the divide within a C program to be run on a CPU, and not an FPGA program. If the incorrect calculations above are repeated with two's complement we'll see that it will now give us the correct results. This way of representing numbers allows addition, subtraction and multiplication to be carried out by the computer in the same way regardless of whether the numbers are signed or unsigned. Note how we were able to go all the way from the smallest to the largest value without having to treat negative values any different. The rest of the positive values follows the same way. If we continue by adding 1 to 1111 it gives us 10000, but since we only use 4 bits the 1 goes away and we get 0000 which codes for 0. For a 4-bit number 1001 codes for -7, 1010 codes for -6, and so on, all the way up to 1111 which codes for -1. The rest of the negative values are ordered such that the nearest higher value can always be found by doing normal binary addition with 1. For a 4-bit number this means that the smallest value is -8 and is stored as 1000. The bit pattern for this value is a one (sign bit = 1) followed by n-1 zeroes. The smallest possible value for an n-bit number with two's complement is -2 ^ n-1. in floating-point numbers) but for whole numbers there is something called two's complement that is almost always used because it solves the problems mentioned here in a relatively easy way. This way of handling negative values can be used in some situations (e.g. It is of course possible to add even more special rules for how the different situations should be handled but it would lead to unnecessary complexity and more expensive hardware. The binary number 1011 can be calculated as follows: The total value of a binary number can thus be calculated by adding all these values for all the bits. The value contributed by an individual bit with the value one in a binary number is 2 ^ b where b is the bit position, counted from right to left, starting from zero. This means that for an n-bit number there are 2 ^ n possible values, but since the counting starts from zero the highest possible value is only 2 ^ n - 1. Since computer memory consist of nothing but ones and zeroes the most natural way to interpret data is to use the binary numeral system. The maximum value that can be stored is about twice as big with unsigned compared to with signed. They can either be interpreted as an unsigned value which means that no negative values are allowed, or they can be interpreted as a signed value which allows both positive and negative values. The bits can be interpreted in two different ways. The most common sizes are 8, 16, 32 and 64 bits. Whole numbers are stored in computers as a series of bits (ones and zeroes) of fixed length.
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