What exactly is an interrupt (for example hardware interrupt or software interrupt). Hear me out. Most sources define an interrupt as when a device sends a signal to the CPU telling it what to do. 1)Anything connected to the computer sends a signal 2)the CPU is always being told what to do. That's what a program is.
So I find the definition basically says nothing.
Last edited by c_weed; 09-30-2014 at 01:49 AM. Reason: added links
A hardware interrupt sequence stops the currently running program and invokes something similar to a call to an interrupt function. A software interrupt is similar to a call being made by the currently running program to call an interrupt function. The details vary depending on the processor. For X86 architecture, there's an array of addresses to handle both hardware and software invoked interrupts. With the early Intel processors, the interrupt handler chip actually emitted two instruction bytes, the first was an interrupt opcode, followed by a single byte value. Later processors ignored the first instruction byte, but had to perform the handshake with the interrupt controller chip which still emitted the interrupt opcode. Current processors just deal with the byte value. IBM mainframes have an array of program control words in low memory in pairs. One of the control words is used to save the current state, and the other control word is used to set the new state (which includes an address). ARM processors switch states from the current state to interrupt or fast interrupt state, which includes some dedicated "shadow" registers.
Many microprocessors have specialized pins that are used trigger a hardware interrupt being generated by "external" hardware, disk drives for example. A software interrupt is generated by software by writing values to addresses designated by the operating system or processor.
You may find this link interesting.
Jim
Last edited by jimblumberg; 09-30-2014 at 06:10 AM.
An interrupt is a seporate bit of program that will execute when a condition is met.
For PIC microprocessors there are lots of different interrupts you can have code for; such as...
Pin Interrupts
Timer Interrupts
Compritor change
USART interrupts (input detected, byte sent)
A/D convertion complete
To name a few...
Here is an example for a UART receive detected:
No matter where my code is, if the hardware detects a UART byte has been received, that code will execute.Code:void interrupt isr(void) { if (PIR1bits.RCIF == 1) { rx_buffer[rx_in_pointer] = RCREG; rx_in_pointer = (rx_in_pointer + 1) % RX_BUFSIZE; } }
Fact - Beethoven wrote his first symphony in C
Some processors, like the X86 family of processors have a interrupt instruction called INT which has single byte operand. As I mentioned in my previous post, for the early X86 processors, like the 8088 or 8086, it was common to use the 8259 chip to handle interrupts. During the interrupt handshake between the 8088/8086 and the 8259, two read cycles occur but the first one is ignored (it may have been the INT opcode in very early chips or prototypes), and on the second read, an 8 bit value is sent from the 8259 to the 8088/8086, which is used to index into an interrupt table. On the older still 8080/8085 cpu's, the 8259 was programmed to work with the 8080/8085, and three read cycles occurred, which was a CALL opcode, followed by two reads to supply a 16 bit address. Getting back to X86 machines in real mode, BIOS and MSDOS "calls" are implemented using the INT instruction.Originally Posted by jimblumberg
The 68000 family of processors has a TRAP (with immediate value for operand) instruction which generates an exception, which is similar to an interrupt. The ARM family of processors has a SWI (SoftWare Interrupt) (with immediate value for operand) instruction. These are mostly used to switch out of user mode into system mode to make operating system calls.
False. What you describe is an interrupt service routine, which is a subroutine typically executed when an interrupt occurs, but does not necessarily have to.
I was wondering where in the code you specify which type of interrupt is associated with the function above? I did some research on the interrupt keyword, and learned about the interrupt vector table, but I couldn't understand how it knows to call your function for a particular interrupt.
WndProc = (2[b] || !(2[b])) ? SufferNobly : TakeArms;
This will vary depending upon compiler, operating system, etc., but it appears in the above code the "interrupt" is the keyword.I was wondering where in the code you specify which type of interrupt is associated with the function above?
Again this varies with compiler, operating system, etc.. But for DOS you need to "install" the interrupt handler, basically placing the address of your function in the interrupt vector table.but I couldn't understand how it knows to call your function for a particular interrupt.
Jim
Usually there is only one interrupt handler that the processor calls at interrupt as far as I know. Of course, many operating systems keep their own "interrupt tables," containing addresses of subroutines that should be called for specific interrupts and delegates them there. Again, this depends on the system in question. This may not hold true for ever system.
If you read it carefully, the first paragraph on the wikipedia link should answer this. It's all about the need to pause execution and give priority to a high-priority request that must take place before execution resumes. They are all signals. But some signals are more important than others.
An interrupt is the old lady or the mother carrying a baby on the bank deposits queue.
Originally Posted by brewbuck:
Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.
When a UART interupt occurs on the PIC microcontroller, the RCIF flag is set in the PIR1 register.
The actual byte is in a register called "RCREG"
I just throw it in a buffer and deal with the input when my processor has time.
This code was for a PIC16F648A
If you wanted to read about this more, look at 12.2.2 here http://ww1.microchip.com/downloads/e...Doc/40044E.pdf
[edit]
And the compiler which I used was the XC8 (it makes a difference how the interupt function is declared)
Section 5.9 http://ww1.microchip.com/downloads/e...Doc/52053B.pdf
[/edit]
Last edited by Click_here; 10-02-2014 at 05:57 AM.
Fact - Beethoven wrote his first symphony in C
It's what Kanye West does when literally anyone else is talking.
What can this strange device be?
When I touch it, it gives forth a sound
It's got wires that vibrate and give music
What can this thing be that I found?
There is usually one interrupt handler for every possible interrupt, if the interrupt is unused then the default handler may be just a "no op" followed a return from interrupt.Usually there is only one interrupt handler that the processor calls at interrupt as far as I know.
On a Windows PC the the BIOS initially handles the interrupt vector table, when the processor is switched to protected mode the operating system takes over this duty with it's own version of the vector table.Of course, many operating systems keep their own "interrupt tables," containing addresses of subroutines that should be called for specific interrupts and delegates them there.
Jim
The PIC has a routine that covers all interrupts (forgetting about priority), and you just look through all the flags to see which one has occured (as explained earlier)
I really like this definition of an interrupt from Gooligum (A tutorial series on how to program PIC microprocessors), even though it is PIC specific...
I thought that I would go through some of the differences in how interrupts are handled in the non-hosted environments.
For something different, I went back to look at the original microcontroller that I learnt on -> The Motorola 68HC11. Freescale 68HC11 - Wikipedia, the free encyclopedia
To set up interrupts on that device, you would put the opcode "JUMP" (7E) and then address of your interrupt service routines in a "interrupt vector". The interrupt takes the program counter to the correct place in the vector table and executes the code. Here is a good explination http://web.alfredstate.edu/albaflr/F...interrupts.pdf
Details on interrupt on that device are here (Section 5.5): http://www.freescale.com/files/micro...t/M68HC11E.pdf
(Note that the chip we were required to use had 256 bytes of EEPROM memory(where your program went) and 512bytes of RAM, so you would always program in assembly language. I have to say that if I had to program in assembly language, I would choose Motorola's instruction set, because of the massive instruction set, it was very easy to make small programs.)
Another example of interrupt is with the AVR.
When programming this, you need to specify the interrupt vector in your ISR (Interrupt Service Routine) -> <avr/interrupt.h>: Interrupts
Behind the scenes, the Atmel behaves like the motorola http://www.atmel.com/Images/io.pdfCode:#include <avr/interrupt.h> ISR(ADC_vect) { // user code here }
And the Arduino (which was built on top of the AVR), All you have to do is attach the interrupt to a function
Arduino - AttachInterrupt
The underlining theme for using interrupts is that the device stops excecuting the program (because of some event), and then using some implementation of interrupt vector table run a ISR, and then return to the main program.
Last edited by Click_here; 10-02-2014 at 07:21 PM.
Fact - Beethoven wrote his first symphony in C
That's interesting. It makes me think of the stuff I've learned studying the Win32 api. I'm guessing that since every window has to register itself, that the ISR involves filling out a message structure, and adding it to the queue of whichever windows are applicable.
WndProc = (2[b] || !(2[b])) ? SufferNobly : TakeArms;
