Requiered a BIOS call for INT from timer in MSX1 and MSX2

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Door sp4

Master (214)

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25-07-2011, 20:23

Hi, i want know what is the BIOS call in MSX1 and MSX2 and the function (or the address) of reply about the INTERRUPT from timer in these two machines.
Nobody can help me to know how is make the INTERRUPT from timer in MSX1 and MSX2 ?
Thanks very muck for the help.

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Van Manuel

Ascended (19270)

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25-07-2011, 21:01

What exactly do you mean?

Van pitpan

Prophet (3155)

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25-07-2011, 22:35

If you want to make it MSX1 compatible, you should use v-blank interruption (every 50th/60th of a second). To do so, you should acknowledge the interrupt and/or hook HTIMI o similar. Enjoy.

Van sp4

Master (214)

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26-07-2011, 12:48

What's the v-blank interruption?
Can you explain more exactly the v-bank interruption?

Van sp4

Master (214)

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26-07-2011, 12:54

I' want know if there is a BIOS call for manage the interrupt from counter, and i want know
what's the function of reply of that INTERRUPT.
Have you understand?

Van pitpan

Prophet (3155)

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27-07-2011, 10:10

Not really, I'm sorry. I'm not following your question. In any case:

xor a
ei
LOOP:
halt
inc a
jr LOOP

This code will increase the A register every 50th or 60th of a second. The "HALT" will effectively halt the computer until the vertical retrace interruption (in the best case scenario) is acknowledged. So, if you want a timer, start coding from here.

Van ro

Scribe (4902)

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27-07-2011, 11:58

ServicePack4: it could be the language barrier that's making your question unclear to us poor souls.
bij default: Whenever MSX generated an interrupt (no matter the source) it "jumps" to address #38. If you have ROM enabled on page 0 (000-3fff) you'll find the defautl interrupt handler routine. It does keyboard mapping, counters and a call to the "hook" (fd9a or fd9f, depending on the source of the interrupt) pitpan mentioned.

disassemble #00038 if you like to see whaz-up.

does that answer ye question, hombre?

Van ro

Scribe (4902)

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27-07-2011, 12:00

oh, and 'v-blank' is short for vertical-blank. It's the interrupt generated at the end of the screen (refresh). So every 50th or 60th (depending on your refresh rate) of a second it'll CALL to #38.

Van sp4

Master (214)

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27-07-2011, 14:00

Thank yuo for your help.
In your reply you tell about ROM enable in page 0. What can I enable this ROM enable?
Are the locations from #00038 address empty or are busy with the default ROM routine?
Can you specify well that detail please?

Van sp4

Master (214)

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27-07-2011, 14:07

Pitpan: does the timer inside the Video Controller connected with the HALT wire of the Z80?

Van ro

Scribe (4902)

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27-07-2011, 14:14

SP4, what's your assembly knowledge skill?

I'm asking 'cuz you ask about some basic-knowledge for asm programmers and it makes me wonder what the heck you want to achieve. are you gonna do some asm coding ?

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