The Intel 8085 is an 8-bit microprocessor introduced by Intel in 1977. It was binary-compatible with the more-famous Intel 8080 but required less supporting hardware, thus allowing simpler and less expensive microcomputer systems to be built.
The "5" in the model number came from the fact that the 8085 requires only a +5-volt (V) power supply rather than the +5V, -5V and +12V supplies the 8080 needed. Both processors were sometimes used in computers running the CP/M operating system, and the 8085 later saw use as a microcontroller, by virtue of its low component count. Both designs were eclipsed for desktop computers by the compatible Zilog Z80, which took over most of the CP/M computer market as well as taking a share of the booming home computer market in the early-to-mid-1980s.
The 8085 had a long life as a controller. Once designed into such products as the DECtape controller and the VT100 video terminal in the late 1970s, it continued to serve for new production throughout the life span of those products (generally longer than the product life of desktop computers).
PIN DIAGRAM OF 8085
BLOCK DIAGRAM OF 8085
The Intel 8255 (or i8255) Programmable Peripheral Interface chip is a peripheral chip originally developed for the Intel 8085 microprocessor, and as such is a member of a large array of such chips, known as the MCS-85 Family. This chip was later also used with the Intel 8086 and its descendants. It was later made (cloned) by many other manufacturers. It is made in DIP 40 and PLCC 44 pins encapsulated versions.
This chip is used to give the CPU access to programmable parallel I/O, and is similar to other such chips like the Motorola 6520 PIA (Peripheral Interface Adapter) the MOS Technology 6522 (Versatile Interface Adapter) and the MOS Technology CIA (Complex Interface Adapter) all developed for the 6502 family. Other such chips are the 2655 Programmable Peripheral Interface from the Signetics 2650 family of microprocessors, the 6820 PIO (Peripheral Input/Output) from the Motorola 6800 family, the Western Design Center WDC 65C21, an enhanced 6520, and many others.
The 8255 is widely used not only in many microcomputer/microcontroller systems especially Z-80 based, home computers such as SV-328 and all MSX, but also in the system board of the best known original IBM-PC, PC/XT, PC/jr, etc. and clones.
However, most often the functionality the 8255 offered is now not implemented with the 8255 chip itself anymore, but is embedded in a larger VLSI chip as a sub function. The 8255 chip itself is still made, and is sometimes used together with a micro controller to expand its I/O capabilities.
PIN DIAGRAM OF 8255
BLOCK DIAGRAM OF 8255
The Intel 8253 PIT is the original timing device used on IBM PC compatibles. It uses a 1.193182 MHz crystal oscillator (one third of the color burst frequency used by NTSC) and contains three timers. Timer 0 is used by Microsoft Windows (uniprocessor) and Linux as a system timer, timer 1 was historically used for dynamic random access memory refreshes and timer 2 for the PC speaker.
BLOCK DIAGRAM OF 8253
The Intel 8259 is a family of Programmable Interrupt Controllers (PICs) designed and developed for use with the Intel 8085 and Intel 8086 8-bit and 16-bit microprocessors. The family originally consisted of the 8259, 8259A, and 8259B PICs, though a number of manufacturers make a wide range of compatible chips today. The 8259 acts as a multiplexer, combining multiple interrupt input sources into a single interrupt output to interrupt a single device.
PIN DIAGRAM OF 8259
BLOCK DIAGRAM OF 8259
Intel 8237 is a family of direct memory access (DMA) chips used in the IBM PC and other systems.
The 8237 DMA Controller supplies the memory and I/O with control signals and memory address information during the DMA transfer. The 8237 is actually a special-purpose microprocessor whose job is high-speed data transfer between memory and the I/O. Although this device may not appear as a discrete component in modern microprocessor-based systems, it does appear within system controller chip sets found in most systems. Although not described because of its complexity, the chip set (82875P ISP or integrated system peripheral controller) and its integral set of two DMA controllers are programmed almost exactly (it does not support memory-to-memory transfers) like the 8237. The ISP also provides a pair of 8259A programmable interrupt controllers for the system.
The 8237 is a four-channel device that is compatible with the 8086/88 microprocessors. The 8237 can be expanded to include any number of DMA channel inputs, although four channels seem to be adequate for many small systems. The 8237 is capable of DMA transfers at rates of up to 1.6M bytes per second. Each channel is capable of addressing a full 64K-byte section of memory and can transfer up to 64K bytes with single programming.
PIN DIAGRAM OF 8237