Assembler for the VIC

[Orangeman96]

In the meantime, and with cartconv in GTK3VICE 3.9, I could successfully make a *.crt file out of the raw binary of MINIMON (download):

Code: Select all

cartconv -t rabbit -i monitor.bin -o minimon.crt -n "VIC-2020 MINIMON" -l $9800

At the moment it is sailing under a false flag - the Rabbit Tape accelerator also puts its firmware at $9800 -, but that's fine for now. Main advantage is, the tool now sits write protected in I/O (which is not the case when soft-loading a *.prg to RAM in I/O).

For those interested, don't bother to use the *.crt file with any VICE version older than 3.9!

It's fantastic, Michael: compact, yet efficient and effective. Thanks much! -OGM

[groepaz]

The firmware chip select logic works quite the same as Rabbit, yes, but the MINIMON cartridge hardware comes with some extras.

Just had a closer look... could you elaborate a bit? I'm not really familiar with VIC20 hardware... and we don't have any freeze logic for VIC20 yet either Is there something like a documentation for programmers? That i could probably read better than schematic.

[Mike]

[...] could you elaborate a bit?

First of all, here is a closeup of the controls on the MINIMON cartridge:



From left to right:

• RESET button - with a short press, upon release, the logic delivers a clean 2 ms reset pulse to both VIC-20 and secondary cartridge.
  A longer press (>1 second) first opens and pulls high the /RESET line in direction to the secondary cartridge (so that cartridge will not be notified later a reset had happened - internal banking logic, say, then retains its state -, then upon button release two things happen simultaneously: the 2 ms reset pulse is delivered (now to the VIC-20 only!) and the /BLK5 signal to the secondary cartridge is also opened and pulled high for roughly 0.3 seconds. During the KERNAL reset routine, an eventually present A0CBM signature will not be found, preventing the autostart of the secondary cartridge. The /BLK5 and /RESET lines will be reconnected to the secondary cartridge after those 0.3 seconds.
• FREEZE - a LED that lights up in blue when reset is pressed for longer than 1 s, indicating the release will perform a freeze reset.
• MON ← I/O → CART switch: the switch in "MON" position maps whatever is put as memory chip in the ZIF socket into the $9800..$9FFF address range. With the switch in CART position, I/O2 and I/O3 are routed straight through to the secondary cartridge. It is in order to change the switch while the VIC-20 is powered on.
• PGM PCT jumper: The PCT position is intended for EPROMs (2716s) or already programmed EEPROMs (2816s or adapted 2864s). With EEPROMs, this setting provides a hardware write protect. The PGM position is intended for RAMs (6116s) or EEPROMs that are supposed to be programmed.

Regarding the "MON ← I/O → CART" switch: it is up to the informed user to decide which position is appropriate. As a rule, when there is any chance that a more complex secondary cartridge might require access to its resources in the I/O area, the switch should be set to the "CART" position. With simpler secondary cartridges, like RAM expanders, the switch can be left in the "MON" position at all times.

Greetings,

Michael

[groepaz]

OK so... looking at this now. Did i understand correctly:

- the MON/CART switch essentially enables/disables the cartridge (which is mapped to IO2/3)
- PGM enables writing to the cartridge (which obviously only works if there is static RAM or EEPROM in the socket)
- Reset (short) is just that, a regular reset
- Reset (long) resets and briefly "disables" a BLK5 cartridge to prevent it from starting. In this case also the "other" cartridge will not "see" reset (how is this even possible? Does the cartridge have a passthrough port?)

correct?

I am struggling a bit with how it even makes sense to support those details in emulation to be honest

[Mike]

- the MON/CART switch essentially enables/disables the cartridge (which is mapped to IO2/3)

In essence, yes. There's circuitry on the cartridge, which arbitrates the I/Ox signals between the ZIF socket and the secondary cartridge.

The reset logic is available all the time.

- PGM enables writing to the cartridge (which obviously only works if there is static RAM or EEPROM in the socket)

Check.

- Reset (short) is just that, a regular reset

Check. To both VIC-20 and secondary cartridge.

- Reset (long) resets and briefly "disables" a BLK5 cartridge to prevent it from starting. In this case also the "other" cartridge will not "see" reset (how is this even possible? Does the cartridge have a passthrough port?)

Yes, see here:

I am struggling a bit with how it even makes sense to support those details in emulation to be honest

From a certain point of view, this cartridge more acts as extension to the VIC-20 mainboard than just as cartridge.

With the switch set to MON, it effectively overlays its memory chip in the ZIF socket in the I/Ox range over whatever is provided by the secondary cartridge. When set to CART, the cartridge acts as a full pass-through to the secondary cartridge, but as said, the reset logic remains active.

[groepaz]

OK, with the passthrough this makes a lot of sense now.

I'll proceed implementing it - however, the cartridge system in xvic is quite simple (compared to x64) right now, "cartridge with passthrough" can't be emulated like this. So this part has to wait for a while - too much other stuff on the TODO list (and this will involve quite a few changes)

[groepaz]

Check r45665 - please test a bit