https://kasraghaffari.com/8-bit daily 0.75 2020-10-14 https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601149436146-6NT7TUZCKKCUAXT2IDK2/image-asset.jpeg 8-bit CPU - Registers Registers temporarily store a single value within them. They are typically split into two categories: General Purpose Registers Special Purpose Registers The only difference between these is that special purpose registers also serve another function besides just storing a value. See the section about the registers below for more details. https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601149388609-1QAGOUDYOVT4XLNFTIZP/image-asset.jpeg 8-bit CPU - Program Counter The program counter has the sole purpose of keeping track of the memory address of the next instruction. After each instruction, the CPU fetches the instruction at the address specified by the program counter. https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601149613609-5JQ4W2EA2DWFSPEOJAIF/image-asset.jpeg 8-bit CPU - 7-Segment Display The seven segment display is attached to a Register O (a special purpose register) and displays the contents of it in either unsigned decimal (0 to 255) or two’s complement decimal (-128 to 127). https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601149355425-B8JUY9ZH8FX7510586LH/image-asset.jpeg 8-bit CPU - Bus The bus is a centralized connection between all the components. Only one component can write to the bus per clock cycle, but multiple components can read the value on the bus. The bus on my 8-bit CPU is 8-bits wide similar to the earliest ISA models. https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601149592456-1OHTYKWTK61OA3OPYTLD/image-asset.jpeg 8-bit CPU - LCD Screen The LCD acts as a write-only special purpose register. It can display any UTF-8 character and can interpret instructions for itself as well (move the cursor, clear the screen, etc). In essence, there is a microcontroller that interfaces with the actual screen and does all the work of displaying text. https://images.squarespace-cdn.com/content/v1/5ec321c2af33de48734cc929/1589847805828-AJIWBELW8MFMGSFE5CQ2/image-asset.jpeg 8-bit CPU - 1 KHz Clock The CPU Clock is essential for the cooperation between the different components of the CPU. Each clock pulse triggers another cycle where information transfer occurs between the components, enabling the execution of instructions. The clock speed determines how fast these pulses occur. In some of the fastest CPUs available on the market, clock speeds can hit upwards of 4+ billion pules per second (4+ GHz) — about 4 million times faster than my 8-bit CPU. https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601149452104-P47UJUO3CDVL3GTLHA74/image-asset.jpeg 8-bit CPU - ALU The Arithmetic Logic Unit (ALU) is the only part of the CPU that does the actual computing. The operations the ALU can do determines what calculations the CPU can do. Some of the most common operations include: bitwise OR/AND/XOR/NOT bitwise shift left/right (circular as well) Addition/Subtraction These operations can be then combined in instructions to do more complex tasks like multiplication, division, and comparisons. My implementation of the ALU has these operations Addition/Subtraction https://images.squarespace-cdn.com/content/v1/5ec321c2af33de48734cc929/1589847895972-04K0P91LO30PWAYK24X3/image-asset.jpeg 8-bit CPU - 1KB RAM Random Access Memory (RAM) is the main component that stores data. Programs are loaded into RAM and then interpreted and executed by the CPU. There are several data structures within RAM, most notably heap and stack, but my build only supports heap. In my 8-bit CPU, the 1KB RAM is split into 4 pages of 256 bytes of RAM. Here, each page represents a different program that is stored within the RAM. The selected program is displayed in binary by LEDs. https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601491621236-GMSUG78NATAWFZXYB3W4/image-asset.jpeg 8-bit CPU - The Pre-Build Before I build, I need to know what to build. https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601492007041-S3EFOF76BQSJWXM6RK0I/image-asset.jpeg 8-bit CPU - The Debugging The longest part https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601491895915-HXFCME9B8HBD2TX5F2JB/image-asset.jpeg 8-bit CPU - The Build Time to finally build everything. https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601492464909-A2D6WU07LE9O90SMC6DL/image-asset.jpeg 8-bit CPU - The Finished Product After months of work… https://kasraghaffari.com/home daily 1.0 2022-05-11 https://images.squarespace-cdn.com/content/v1/5f6f62b78ed7155b91abc5d0/1601148424550-A17Z2U3GP4ZS00QR4Z2Q/image-asset.jpeg Home - Projects I have had a lot of time on my hands, and I’ve used it well. 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