Full Form of RST, Types of Interrupts
Girijesh Singh10 Nov, 2023
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RST stands for restart, and in terms of technology, we have the term RSTn. RSTn stands for restart instruction. It is a type of interruption to the microprocessor performing a particular task. In other words, it is the method of creating a temporary halt during program execution that allows peripheral devices to access the microprocessor. RSTn are 1-byte call instructions.
Types of Interrupts
There are different types of interrupts that allow temporary pauses in the microprocessor. INTERRUPTS ___________|____________ | | HARDWARE SOFTWARE INTERRUPT INTERRUPT _______|_________ | | MASKABLE NON- MASKABLE1. Hardware and software interrupts.
On the basis of attachment points, we classify the interrupts into these two categories. Inside a microprocessor, when a program causes an interruption, that kind of interrupt is called a software interrupt. There are 8 such interrupts. For example - from RST 0 to RST 7. On the contrary, hardware interrupts are the physical transmission of interrupts through the attached pins of the microprocessor. Examples of the same are TRAP, INTR, RST5.5, RST6.5 and RST 7.52. Vectored and non-vectored interrupts.
On the basis of vector addresses, these are classified into two categories. Vectored interrupts hold a fixed address and a predefined service routine to execute the interruption. All the above-mentioned RST interrupts are examples of vector interrupts, except INTR. On the other hand, a non-vectored interrupt is when the vector address of the interrupt service routine corresponding to the INTR interrupt is not well known to the microprocessor, but rather it is provided by the external hardware/peripheral.3. Maskable interrupt and non-maskable interrupt
A further categorization done under hardware interrupts gives us maskable and non- maskable interrupts. For example, TRAP is a non-maskable interrupt, and INTR, RST 5.5, RST 6.5, and RST 7.5 are maskable interrupts. A non-maskable interrupt means the interrupts cannot be masked and are unavoidable, and the service routine has to serve the interrupt. On the other hand, maskable interrupts are those that can be avoided and masked. For instance, if a masked interrupt comes in between the execution of the main program, it will not hinder the execution of the main programme. RST 5.5 It is an interrupt that, when executed, commands the processor to save the contents of the PC register into the stack and branches to the particular 002CH address. Additionally, it is a sensitive level input, but with a lower priority than RST 6.5 and RST 7.5. RST 6.5 Here, this interrupt commands the processor to save the PC register into the 0034 H address's stack and branches. It has a priority higher than RST 5.5 and lower than RST 7.5. It is a maskable interrupt. Moreover, it causes an internal restart to be inserted automatically. RST 7.5 Commands the processor to save the PC register unto 003 CH address's stack and branches. Also, It is an edge-sensitive interrupt. [wp-faq-schema title=" Full Form of RST FAQs" accordion=1]Is there any priority order in the execution of interrupts on a microprocessor?
Yes, the priority in cases of hardware interrupts is as follows- Highest - TRAP > RST 7.5 > RST 6.5 > RST 5.5 > INTR - Lowest
What are the types of RST?
RST are numbered from 0 to 7 ( software interrupts) and also as 5.5, 6.5, and 7.5 (hardware interrupts). The numbers designated are used to define an address point using binary numbers and are of the size of 1 byte.
What is the need for interrupts in microprocessors?
Interrupts send signals from a peripheral device to the processor to perform a task in between the main programme run by the microprocessor. Interestingly, it temporarily halts the execution of the main programme.
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