Re: 6502 BE function ?

["Richard A. Cini" <rcini@msn.com>]

You may also want to look at the schematics for the VIC-20. The 6502 shared
the address and data busses with the 6560 VIC chip. I believe that the 6560
shared the address buss on the processor Phase 0 clock (pin 37).

Rich

-----------------------------------
[  Rich Cini/WUGNET
[   ClubWin!/CW7
[   MCP Windows 95/Windows Networking
[   Collector of "classic" computers
[   http://highgate.comm.sfu.ca/~rcini/classiccmp/
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Patrick Schaefer <pa.schaefer@fz-juelich.de> wrote in message
37D68CD5.3281@fz-juelich.de">news:37D68CD5.3281@fz-juelich.de...
> friedt@lpmo.univ-fcomte.fr wrote:
> >
> > As I do not have a datasheet of the original 6502, I am unable to figure
out
> > how to set its data bus, @ bus and R/W# to hiZ state. Is that done using
the
> > BE (bus enable) pin ?
>
> There is no bus enable. Usually pin 1 is connected to ground.
>
> For a DMA circuit with bus hold get a copy of the Apple II Reference
> Manual and look how the cpu section is designed. Basically you have to
> set the RDY line low and disconnect the address bus using tristate
> buffers.
>
> There is a maximum time for the cpu to be stopped, after this time it
> will need a reset to recover.
>
>
> Patrick