Image Map Image Map
Page 3 of 3 FirstFirst 123
Results 21 to 23 of 23

Thread: Fun with CC40's

  1. #21

    Default

    Quote Originally Posted by smp View Post
    By any chance, would your memory board work in a TI-74? Looks like a different form factor, but perhaps a converter to the TI-74 could be rigged up?
    Not at present, but I can design a specific unit for the 74. The main problem is that one needs to find a source for the connectors for the 74.

    PS: I have a large text file of CC-40 info by Dan Eicher dated 12/1/96. Have you seen that? It appears to have a wealth of info about interfacing to the CC-40 from back then.
    Yep, dloaded it when I started on my efforts. It is missing a few items:

    • Pin 3 and 17 are listed as unknown, but JGardner's info notes they are PORT 25.2 and .3
    • ALATCH + .. is !OE
    • !WE is not defined (I found it by reverse engineering the RAM cart)
    • A14 is shown inverted, but putting the cc40 on my scope does not show any such inversion.

  2. #22

    Default

    Quote Originally Posted by JGardner View Post
    Brain -

    The article referenced by SMB is here:

    http://ftp.whtech.com/hexbus_cc40_ti...4%20hexbus.txt

    Bits 2 & 3 of the Peripheral File register P25 control the cartridge paging

    bits present on pin 3 & pin 39 of the cartridge port.
    Understood, but I am trying to sort out how it was decided that the two bits were to be used for paging. Are there routines in the ROM using them in that way?


    SMB -

    There are no equivalent paging bits present in the '74 cartridge port.

    However Multi-page cartridges could be enabled by latching <Writes> to

    a chosen address (>BFFF comes to mind) for use as the High Address for

    a multi-page cartridge. The real problem is the unobtainable (AFAIK) '74

    port connector (except by cannibalizing an existing cartridge)...

    Hope this helps.

    Jack
    I'm less concerned about paging bits, as I have created a 512kB ROM/512kB RAM cart that includes a small CPLD. Since all signals are present on the bus, it is trivial to decode a specific address (not in the CART ROM or CART RAM space) and use that register to bank the RAM and ROM. Any externally accessible memory location can be used.

    I have a few goals:

    • create 2 banking registers. One for the lower 16kB of memory, and one for the upper
    • Create a config register for the two banks (00 = nothing,, 01 = rw ram, 10 = read only ram, 11 = rom)
    • See if I can map memory into the various unused places in the memory map from the cartridge space, to completely fill the unit with RAM

  3. #23

    Default

    I added some .02 to the CC-40 thread on Atariage:

    http://atariage.com/forums/topic/255...c40/?p=3905368

    I'm not quite too sure how it did it, but the Editor Assembler cart was 64K and was paged between two 32K banks. Ksarul will have to tell us how A15 was hooked up, but the cart was super simple. One EPROM and one resistor. I'm guessing one of the CC-40 pins was hooked up to A15 on the 27512, and toggled it somehow to switch between the two 32K banks.

    Once switched though, if I remember how I dumped it correctly, it stayed in that 32K bank when you quit the program. When you ran the other program in the cart, it switched banks and ran it. Part of the cart has Editor Assembler and part of the cart has Memo Processor. My guess is that they had to modify the cartridge header in both carts, or that the CC-40's ROM by default can scan multiple banks for the program headers itself (and in this case, I'd have to do a DIFF on Memo Processor in EA vs Memo Processor stand alone to prove it's the same or not.)

    Edit: The memo processor binaries in the stand alone and the EA cart are both identical. I'm surmising the CC-40 ROM can do paging built in and determine if there are multiple 32K banks to scan. To prove or disprove this, we would have to put two 32K images in a 64K EPROM and hook it up like the EA cart and see if it actually will run either program.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •