On Fri, Nov 30, 2018 at 12:48:17AM +0100, silverdr@wfmh.org.pl wrote: > I've got a question I can't answer out of my head and can't currently set any test bench for - how does the 6502 and 6510 behave when it comes to getting off the bus. I know we can make 6510 off the address bus with the additional line that is not available in 6502 but the question is: does any of the two (especially 6510, which surely has the ability) get off the bus by itself like during other phase of the clock cycle? The 6502 always drives all address pins. The 6510 whenever AEC is high. > IOW - if put into a tight loop like: > > 1000 - JMP $1000 > > will all the address lines (except the two lowest ones, obviously) remain unchanged and continuously driven by the CPU? Or will those only be driven during active clock phase? On a 6502: yes. On a 6510: AEC is an *input*. For example on the C64 it is driven by the VIC-II, and that pulls AEC low every first half clock, and those second half clocks it steals, too. AEC also control R/#W and the data bus (which of course the 6510 only drives whenever it is writing to memory). SegherReceived on 2018-11-30 09:00:02
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