First Class Fitness

IT Management

Consider a system built around an 8-bit microprocessor. This will be a CPU address bus of 16 bits, allowing direct 64 kibibytes (KiB) of memory. In this system, the first 32 KiB of address space would be allocated to RAM, a further 16 KiB ROM and the remaining space to other devices such as timers, counters, chips, displays video, sound generating devices, etc.. The hardware of this system is organized so that the devices on the address bus will only respond to directions which will be provided for them and all other addresses will be ignored. This is the work of decoder addresses and this is what will set the system memory map.
In this way we would end up with a memory map like this:
Note that this memory map contains gaps, which is fairly common.
Assuming the controller fourth record video sets the background color of the screen, the CPU can set this color by entering a value in the A003 position using your standard of writing instruction. Using the same method taps can be displayed on screen by typing values of characters in a special area of RAM within the video controller. Because of its low cost will allow the RAM bit-mapped displays.