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Old 17 January 2018, 01:21   #1
bloodline
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CIA interrupts...

When the CIA generates an interrupt, does it signal the CPU directly, or does it write to the INTREQ register?
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Old 17 January 2018, 07:46   #2
Toni Wilen
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INTREQ. All interrupt lines are connected to Paula. Paula sends currently active 3 bit interrupt level signal to the CPU.
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Old 17 January 2018, 08:19   #3
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Great! Thanks Toni
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Old 17 January 2018, 09:50   #4
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Quote:
Originally Posted by Toni Wilen View Post
INTREQ. All interrupt lines are connected to Paula. Paula sends currently active 3 bit interrupt level signal to the CPU.
So when the CPU responds to a Ports/Timer interrupt, it must both read the CIA ICR and clear the relevant bit in the INTREQ?

Also the CIA A Inmodes: I know that O2 is 10th of the 7Mhz clock, what freq is the other Mode?
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Old 17 January 2018, 09:54   #5
Toni Wilen
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So when the CPU responds to a Ports/Timer interrupt, it must both read the CIA ICR and clear the relevant bit in the INTREQ?
Yes, in that order or you get same interrupt twice.
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Old 17 January 2018, 14:49   #6
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Also the CIA A Inmodes: I know that O2 is 10th of the 7Mhz clock, what freq is the other Mode?
The CIA can also count positive transitions of the CNT pin. For the CIA-A, I think CNT should be connected to the keyboard clock line, which is also used as clock for receiving key codes on the serial port.
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Old 18 January 2018, 10:33   #7
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The CIA can also count positive transitions of the CNT pin. For the CIA-A, I think CNT should be connected to the keyboard clock line, which is also used as clock for receiving key codes on the serial port.
I forgot the keyboard would have a clock too! Cheers!
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