ocr: THE EXPANSION BUS (Continued) Ifa proper DMA is asserted, the C64 tri-states and shuts down, allowing the DMA source complete access to the processor bus. Such a DMA source must monitor the 02 and BA outputs, as it must tri-state when the VIC is on the bus, and it must completely DMA when a VIC DMA is called for. The VIC chip always has the highest DMA priority. When on the bus, the DMA sourçe has access to RAM, ROM, and 1/O in the C64 DMA scheme. A proper DMA shutdown is usually achieved via some C64 software handshaking with the DMA source. The C128 mode uses a similar DMA scheme. When the D ...
