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The Intel 8085 ("eighty-eighty-five") is an 8-bit microprocessor produced by Intel and introduced in March 1976. [2] It is the last 8-bit microprocessor developed by Intel. It is software-binary compatible with the more-famous Intel 8080 with only two minor instructions added to support its added interrupt and serial input/output features.
In computer systems programming, an interrupt handler, also known as an interrupt service routine or ISR, is a special block of code associated with a specific interrupt condition. Interrupt handlers are initiated by hardware interrupts, software interrupt instructions, or software exceptions , and are used for implementing device drivers or ...
A hardware interrupt is a condition related to the state of the hardware that may be signaled by an external hardware device, e.g., an interrupt request (IRQ) line on a PC, or detected by devices embedded in processor logic (e.g., the CPU timer in IBM System/370), to communicate that the device needs attention from the operating system (OS) [7] or, if there is no OS, from the bare metal ...
Diagram about the course of an interrupt routine. In a computer, an interrupt request (or IRQ) is a hardware signal sent to the processor that temporarily stops a running program and allows a special program, an interrupt handler, to run instead.
The 8259 may be configured to work with an 8080/8085 or an 8086/8088. On the 8086/8088, the interrupt controller will provide an interrupt number on the data bus when an interrupt occurs. The interrupt cycle of the 8080/8085 will issue three bytes on the data bus (corresponding to a CALL instruction in the 8080/8085 instruction set).
For the "interrupt acknowledge" method, the external device gives the CPU an interrupt handler number. The interrupt acknowledge method is used by the Intel Pentium and many older microprocessors. [8] When the CPU is affected by an interrupt, it looks up the interrupt handler in the interrupt vector table, and transfers control to it.
An end of interrupt (EOI) is a computing signal sent to a programmable interrupt controller (PIC) to indicate the completion of interrupt processing for a given interrupt. Interrupts are used to facilitate hardware signals sent to the processor that temporarily stop a running program and allow a special program, an interrupt handler, to run ...
FLAGS registers can be moved from or to the stack. This is part of the job of saving and restoring CPU context, against a routine such as an interrupt service routine whose changes to registers should not be seen by the calling code. Here are the relevant instructions: The PUSHF and POPF instructions transfer the 16-bit FLAGS register.