External Interrupt - Revision history

MacDeath at 20:08, 17 December 2010

2010-12-17T20:08:52Z

Arnoldemu: /* External Interrupt (INT Pin) */

2010-06-21T09:10:04Z

‎External Interrupt (INT Pin)

Arnoldemu: /* External Interrupt (INT Pin) */

2010-06-21T09:05:46Z

‎External Interrupt (INT Pin)

Nocash: Created page with '== External Interrupt (INT Pin) == The INT signal is internally used by the CPC (triggered at 300Hz, and divided by software to get 50Hz/60Hz Video interrupts). The BIOS does co…'

2010-06-18T19:42:43Z

Created page with '== External Interrupt (INT Pin) == The INT signal is internally used by the CPC (triggered at 300Hz, and divided by software to get 50Hz/60Hz Video interrupts). The BIOS does co…'

New page

== External Interrupt (INT Pin) ==

The INT signal is internally used by the CPC (triggered at 300Hz, and divided by software to get 50Hz/60Hz Video interrupts). The BIOS does contain some provisions for sharing the INT signal with external interrupts. However, most peripherals are using [[NMI]]'s, which don't require to recurse conflicts with internal INTs.

Peripherals that do use external INTs:
* [[Music Machine]] - accordingly to the manual: It can "disable" the internal interrupt, and replace it by external MIDI/ACIA interrupt. ''Unknown if/how it is really doing that, "disabling" the internal interrupt could be probably done only "shortcutting" the INT signal to 5V, which would be a rather aggressive solution - so maybe the manual only meant that software "ignores" the internal interrupt (?) - also, it referred to IRQ, which could eventually also mean NMI rather than INT...? - the Music Machine software isn't in the internet yet, so one can't disassemble/verify this.''

== See also ==

* [[NMI]] - Non-maskable Interrupts (more commonly used by peripherals)

← Older revision		Revision as of 20:08, 17 December 2010
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	* [[NMI]] - Non-maskable Interrupts (more commonly used by peripherals)		* [[NMI]] - Non-maskable Interrupts (more commonly used by peripherals)
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		+	[[Category:Programming]]

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 The gate-array interrupt is automatically acknowledged and cleared, so external maskable interrupts should only be cleared explicitly by the Z80 performing an I/O instruction, otherwise they would conflict with the gate-array interrupt and you would not know the source of the interrupt.
-(This information is mentioned in SOFT968).
+SOFT968 Section 11 "Interrupts" mentions this.
 == See also ==
 * [[NMI]] - Non-maskable Interrupts (more commonly used by peripherals)

@@ Line 5: / Line 5: @@
 Peripherals that do use external INTs:
 * [[Music Machine]] - accordingly to the manual: It can "disable" the internal interrupt, and replace it by external MIDI/ACIA interrupt. ''Unknown if/how it is really doing that, "disabling" the internal interrupt could be probably done only "shortcutting" the INT signal to 5V, which would be a rather aggressive solution - so maybe the manual only meant that software "ignores" the internal interrupt (?) - also, it referred to IRQ, which could eventually also mean NMI rather than INT...? - the Music Machine software isn't in the internet yet, so one can't disassemble/verify this.''
 == See also ==
 * [[NMI]] - Non-maskable Interrupts (more commonly used by peripherals)