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ASIC IVR bit 0? Anyone know this?
The ASIC uses the IVR in combination with the DCSR (DMA Control/Status register) to place a value on the data bus during an interrupt. From the documentation I've read, the Z80 ignores bit D0 during an IM2 interrupt vector lookup, but this isn't the case in IM0. Further testing needs to be done in order to determine what the ASIC actually places in bit D0 during an interrupt. This bit is also used to automatically clear DMA interrupts when set to 0. Testing IM0 interrupts shouldn't be a hard task, I will do it as soon as possible, unless someone already knows the answer? [[User:Executioner|Executioner]] 01:00, 27 July 2007 (CEST)
