As my early post we discussed what are Interrupts in microprocessor 8085? Now in this post we will see Interrupt Structure in 8085 microprocessor. Interrupt is the mechanism by which the processor is made to transfer control from its current program execution to another program having higher priority checking. Now question is how processor get those interrupt and form where? The interrupt signal may be given to the processor by any external peripheral device to different interrupts pin in 8085 microprocessor. The program or the routine that is executed upon interrupt is called interrupt service routine (ISR). After execution of ISR, the processor must return to the interrupted program. Key features in the interrupt structure of any microprocessor are as follows:
- Number and types of interrupt signals available.
- The address of the memory where the ISR is located for a particular interrupt signal. This address is called interrupt vector address (IVA).
- Masking and unmasking feature of the interrupt signals.
- Priority among the interrupts.
- Timing of the interrupt signals.
- Handling and storing of information about the interrupt program (status information).
When we discussed on Interrupt Structure in 8085 microprocessor then we should know that wht are the different type of interrupt present in 8085 microprocessor?
Types of Interrupts:
Interrupts are classified based on their maskability, IVA and source. They are classified as:
- Vectored and Non-Vectored Interrupts
- Vectored interrupts require the IVA to be supplied by the external device that gives the interrupt signal. This technique is vectoring, is implemented in number of ways.
- Non-vectored interrupts have fixed IVA for ISRs of different interrupt signals.
- Maskable and Non-Maskable Interrupts
- Maskable interrupts are interrupts that can be blocked. Masking can be done by software or hardware means.
- Non-maskable interrupts are interrupts that are always recognized; the corresponding ISRs are executed.
- Software and Hardware Interrupts
- Software interrupts are special instructions, after execution transfer the control to predefined ISR.
- Hardware interrupts are signals given to the processor, for recognition as an interrupt and execution of the corresponding ISR.