IRQ - INTERRUPT MADE ABSOLUTELY EASY WITH C128
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TOOL: 		C128 - Built-In ML-Monitor and BASIC 7.0 {Commodore C128}
Language: 	Assembler / BASIC 7.0
Extra:		None
Author: 	Misel Zivanovic
Note:		(C) 12th DEC 2025 - www.lived.ch, mzretro.ch
Information: 	I guess every C128 owner want to see IRQ their own IRQ in action!
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Now you'll see why it is important to know what goes where!
We have 2 identical lines of code {same commands}, however slightly re-arranged and that
is then showing effects.

As you will see, both code examples are going to deliver the same result, but with one
major difference. 

Example one isn't permanent change, it's just temporary!
It means you can change text color {cursor}, background and border color.
While the 2nd example will not allow you to do that.  
It will look like the system is ignoring your requests!

And we learned something again, nice!
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EXAMPLE 1:
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d 1300 1320
. 01300  78       sei
. 01301  a9 1b    lda #$1b
. 01303  8d 14 03 sta $0314
. 01306  a9 13    lda #$13
. 01308  8d 15 03 sta $0315
. 0130b  a9 0b    lda #$0b
. 0130d  85 f1    sta $f1
. 0130f  a9 08    lda #$08
. 01311  8d 20 d0 sta $d020
. 01314  a9 09    lda #$09
. 01316  8d 21 d0 sta $d021
. 01319  58       cli
. 0131a  60       rts
. 0131b  4c 65 fa jmp $fa65

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ALL EXPLAINED:

. 01300  78       sei		Set Interrupt Disable Flag {System ignores interrupts until we set new one, meaning clear the flag}
. 01301  a9 1b    lda #$1b	This is the LOW Byte {Target address}
. 01303  8d 14 03 sta $0314	Write to IRQ Vector
. 01306  a9 13    lda #$13	This is the HIGH Byte {Target address}
. 01308  8d 15 03 sta $0315	Write to IRQ
. 0130b  a9 0b    lda #$0b	Dark-Grey for the
. 0130d  85 f1    sta $f1	Cursor
. 0130f  a9 08    lda #$08	Color for the
. 01311  8d 20 d0 sta $d020	border
. 01314  a9 09    lda #$09	Color for the
. 01316  8d 21 d0 sta $d021	background
. 01319  58       cli		Clear Interrupt Disable Flag
. 0131a  60       rts		Return To Subroutine or here back to BASIC when called from BASIC
. 0131b  4c 65 fa jmp $fa65 	The normal IRQ interrupt handling routine
				{Restore normal IRQ functions}

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MACHINE-LANGUAGE-MONITOR CODE LISTING:

{If you paste this code in ML-Monitor of C128, then you can avoid manual corrections which}
{are practically mandatory when you paste the assembled code from above}
{This below is exactly the same code as above!}
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m 1300 1320 {EXAMPLE 1}

>01300 78 a9 1b 8d 14 03 a9 13:XI....I.
>01308 8d 15 03 a9 0b 85 f1 a9:...I..QI
>01310 08 8d 20 d0 a9 09 8d 21:.. PI..!
>01318 d0 58 60 4c 65 fa 00 fa:Px.lEZ.Z
>01320 00 00 00 00 00 00 00 00:........

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EXAMPLE 2:
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This example will not allow you any kind of modification in regard of text color,
background or border color!

Your input will be ignored! Easy done!
{And if you, in addition to this, disable the RESTORE Key, dann this change will be}
{practically permanent until the reset button is pressed}

d 1300 131e

. 01300  78       sei
. 01301  a9 0d    lda #$0d
. 01303  8d 14 03 sta $0314
. 01306  a9 13    lda #$13
. 01308  8d 15 03 sta $0315
. 0130b  58       cli
. 0130c  60       rts
. 0130d  a9 0b    lda #$0b
. 0130f  85 f1    sta $f1
. 01311  a9 08    lda #$08
. 01313  8d 20 d0 sta $d020
. 01316  a9 09    lda #$09
. 01318  8d 21 d0 sta $d021
. 0131b  4c 65 fa jmp $fa65
. 0131e  00       brk

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MACHINE-LANGUAGE-MONITOR CODE LISTING:

{If you paste this code into ML-Monitor of C128, then you can avoid manual corrections which}
{are practically mandatory when you paste the assembled code from above}
{This below is exactly the same code as above!}
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m 1300 131e {EXAMPLE 2}

>01300 78 a9 0d 8d 14 03 a9 13:XI....I.
>01308 8d 15 03 58 60 a9 0b 85:...x.I..
>01310 f1 a9 08 8d 20 d0 a9 09:QI.. PI.
>01318 8d 21 d0 4c 65 fa 00 00:.!PlEZ..

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