Is possible to turn off/pause 6502 by any exp. port pin?

[MIRKOSOFT]

Hi!

I'm still new.
First I needed to know that 6502 in VIC20 is different to 6510 in C64 or 8502 in C128.
I know difference.

I want to ask if is possible to turn off/pause 6502 CPU by any expansion port signal in IO space.
Is it possible?

Why:
I'm discovering two things:
1. SCPU64 and SCPU128 are connected by expansion port, but 128 version has own MMU and wires to 8502 CPU - it is easy to turn them on/off by switch. I owned SCPU128
2. CP/M Cartridge for C64 or C128 - without any wires uses similar software method. I own one.

I found Z80 Videopak for VIC20 what is 80 column card + Z80 CPU and memory expansion.
I think it does it similar way.
Really if anybody owns it, I want to buy it 100%.
I have purposes why I'm asking which are for now not public.

Thank you for help.
Miro

[srowe]

The 6502 has a RDY pin that was designed for single stepping but it is hardwired with a pull-up resistor on the VIC-20.

[Mike]

[...] Z80 Videopak for VIC20 [...]

Please cite a reliable source for this.

A search for "Z80 Videopak" only turns up with a Z80 cartridge of that name for the C64.

There exist several 40/80 column cards for VIC-20, some of them of German production, labeled with "80Z-Karte" or the like ("Z" as German shortcut for Zeichen, literally character(s) or column(s) in the context here). Which might be a likely source of confusion between "Z80" and "80Z". None of those 40/80 column cards I know has a Z80 CPU on board.

Besides, the 6502 is busmaster on the cartridge expansion port. As srowe wrote, there's no way to stop the 6502 from the outside. Also the address lines cannot be tristated and the data lines have to honour whatever is indicated as read/write on the VR/W or CR/W signals. Regardless what's in a VIC-20 cartridge, it only ever appears as (banked) RAM or ROM expansion, possibly with I/O registers (at $9800..$9FFF), eventually capable of issuing interrupts (IRQ or NMI). That's it. No way to "take over" the VIC-20 from the outside.

This doesn't rule out a co-processor card for the VIC-20, but it would have to operate mainly on its own and would only be able to use the VIC-20 as terminal.

[MIRKOSOFT]

I'm sorry for Z80 Videopak and really is for C64.
But I collected info about Z80 and 80 column cards long time ago and there found my mistake.
Here are collected info (I can add pictures and manuals to some of them:

BI-80 uses MOS6545 incl. RAM Expansion and Basic 4.0 by Batteries Included
C64 80 COLUMN CARD uses MOS6545 or MOS8563R9 (schematics 6545 / photo 8563R9) by Commodore
EX80 uses MC6845 by MK Datentechnik
EX80 uses MC6845 by Jann Datentechnik incl. Character Editor
EX80 Plus incl. Protext 80
Protecto 80 uses MC6845 by Protecto Enterprizes
Protecto 40/80 uses MC6845 by Protecto Enterprizes (VIC20)
Z80 Videopak 80 uses ? incl. Z80 CPU by Data 20 (monochrome black & white, video out to Videopak 80 and out 5-pin DIN to monitor)
Videopak 80 by Data 20
XL 80 by Data 20 incl. Wordmanager and Copier
Zero 80 uses MC6845 by ROOS incl. Textveraiberter, spreadsheet & internal RTC (possible picture mix)
Zero 40/80 by ROOS (VIC20)
Maxi by Data Becker
80-Zeichenkarteby DELA
ZK-80 Plus by Decam Messgeräte
80-Zeichenmodul by Print-Technik
Kalawsky 40/80 incl. RAM Expansion (VIC20)
Tseng PET Graphics Board