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The interface is very simple; just the two connectors, a few wires and two small (68 and 82 ohm) resistors. I wired up one last Friday and tried. It works very well:
Very interesting. Do you have a wiring diagram with the connector pin numbers?
what wedge functions would be useful ?
Dan: Good luck building the adapter. It was rather straightforward. Right now you'll need an EPROM programmer and replace the Kernel chip to use it. My CBM 610 was already modified for Swedish keyboard so it has adapters from 24-pin ROMs to 28-pin 2764 EPROMs. It made the change of Kernel very simple. If your B128 machine is original, you may find actual ROMs inside that would require an EPROM adapter. If you're really unlucky, the chips may even be soldered so the cartridge solution (not yet realized) would be the only feasible way to complete the task.
That probably would be the difference, to add one or more devices without putting more strain to the CIA chip.
I have been looking for a way to connect the two printers I use on my system setup.I have three drives connected to the serial bus (1541, 1571 and 1581). To operate the printer(s), I have to remove two of the drives because of excessive load on the serial bus.
If we could just get Dan to give up fishing, we'd get a lot more work out of him.
Last week, I came across Ullrich von Bassewitz' adapter for the CBM-II series computer, which lets one attach a 1541 floppy drive to the otheriwse unused cassette port. It requires installing a custom Kernel though.http://zimmers.net/anonftp/pub/cbm/b/kernal610-new.zipThe interface is very simple; just the two connectors, a few wires and two small (68 and 82 ohm) resistors. I wired up one last Friday and tried. Steve Gray and me have discussed the possibility to extract Uz' driver code to a cartridge image, as I have access to a small surplus of B128 cartridges fitted with two socketed 2764 each, for a total of 16K. If we advance with this, I think at least a DOS wedge would be required. To implement JiffyDOS for the B128 however may be a bit too advanced...As a side note, it was speculated whether this kind of adapter would work with PETs, and of course VIC-20 and C64/128 if you want an additional IEC port. It is just a matter of writing/adapting the driver code. I would suppose someone in time has already done this for the PET? In particular as most PETs have room for utility ROM expansion, it would be very handy to have a driver to let you connect 1541 like drives.
Yay! I had forgotten about that, although admittingly it isn't on the top of my priority list. On the mailing list, Uz mentioned the IEC routines came from the Protext cartridge, whether that was a CBM-II product or some other Commodore computer. There is a cartridge called ProfiText mapping in at $2000. It might be worth disassembling to see if the same routines exist in that binary, and perhaps even easier to extract from.http://zimmers.net/anonftp/pub/cbm/firmware/computers/b/index.html
Pin Type | Pin Type 1 A0 | A BD0 2 A1 | B BD1 3 A2 | C BD2 4 A3 | D BD3 5 A4 | E BD4 6 A5 | F BD5 7 A6 | H BD6 8 A7 | J BD7 9 A8 | K GND10 A9 | L GND11 A10 | M SR/W12 A11 | N S0213 A12 | P NOT CSBANK114 +5V | R NOT CSBANK215 +5V | S NOT CSBANK3
Actually I was wrong last night. The IEC routines already are included in the 8K binary. The reference to $6000 says where the ROM image should end, i.e. fill up to 8192 bytes.The reason why I didn't get much action was because I tried with my uIEC which is set to device 9. There is a command UNIT in the machine code monitor. It takes a two digit decimal number, i.e. "UNIT 09" to switch the device number.I can now read directories and hopefully load files from the IEC unit inside the monitor. However upon exit, the routines are disabled. I'll try later to put together a subset of the routines which at least allows one to SYS the IEC routines into place and back. Autostart might be nice, but so far I haven't seen any B-series cartridge implementing autostart. I read yesterday briefly what it takes to get it to work, so I suppose it is technically possible...
I wonder if there is any way to use the emulator for development purposes. While it won't have the hardware support for an IEC unit, we know that code already works so it is more a matter that the computer won't crash in the middle of operation. Otherwise it will be quite cumbersome to program and erase EPROMs all the time, even if one has a cache of 5-10 chips to recyle.