[Coco] Re: 6309 microprocessor project: 11-01-2003

[Rodney V Hamilton]

In article <1g3t8zp.12zr0dfu6ebwgM%tlindner at ix.netcom.com>, 
tlindner at ix.netcom.com says...
>John Collyer <johncollyer at zoominternet.net> wrote:
[snip]
>> Also I'd like to learn more about the Multi-Pak and how it switched
>> between rom cartridges?
>
>The entire bus is shared (unswitched) between the four ports except the
>following three lines:
>
>SCS (CoCo pin number 36)
>CTS (CoCo pin number 32)
>Cart (CoCo pin number 8)
>
>On power up the front switch determines which of the four slots these
>three lines are connected to. But writing to the location $ff7f can
>change the behiavor:
>
>76543210
>\  /\/\/
> \/  | |
>  |  | +--- SCS slot number
>  |  +----- CTS slot number
>  +-------- Ignored
>
>Also the Cart signal is selected by bits 1 and 0 or bits 3 and 2, but
>for the life of me I can't remember which. Any help is appreciated.

The CART signal is also switched by the CTS control bits, according to
the Multi-Pak service manual.  Also, the bits are arranged this way:

 76543210
 \/\/\/\/
  | | | |
  | | | +--- SCS* slot select
  | | +----- ck1/ck0 (unused)
  | +------- CTS*/CART* slot select
  +--------- ck3/ck2 (unused)

The four "ck" bits are unused in the multi-pak but may be written/read
to test the operation of the select latch. (from page 31 & schematic)

Rodney