Re: 6569 luminances

----- Original Message ----- 
From: "Gerrit Heitsch" <gerrit@laosinh.s.bawue.de>
Sent: Monday, May 14, 2012 6:56 AM

> As for the ROMs... you could desolder all of them, and add a little
> adapter with a 74LS11 and a properly programmed 27C256 on it.
-------
One of Jim Brain's 2364 adapter boards ($1.50, $5.00 assembled) is ideal for
this; just add some diodes and a pull-up resistor to wire-AND the /CEs.
http://store.go4retro.com/2364-adapter/

Haven't looked at it yet but his new 23XX adapter might make it even easier:
http://www.go4retro.com/products/23xx-adapter/

BTW, if you're patient Futurlec also has reasonably priced 2114s and 4164s:
http://www.futurlec.com/ICRAM.shtml

**********************************************************

> As for the ROMs... you could desolder all of them, and add a little
> adapter with a 74LS11 and a properly programmed 27C256 on it. Then you
> have all 3 ROMs in a single CMOS-EPROM which needs a lot less power,
> especially if in standby (_CS high).
>
> Setup:
>
> - Build an adapter to use a 27xxx-EPROM in the socket of a 24pin 2364 ROM.
> Most of it is 1:1, just a few lines need to be rerouted. Do not connect
> the _CS line directly. Place it either into the KERNAL or BASIC socket.
>
> - Connect all 3 _CS signals for the ROMs to the 3 inputs of one of the
> gates of the 74LS11. The output goes to _CS and _OE of the EPROM.
>
> - Also connect two of the _CS-Signals to A13 and A14 of the EPROM.
>
> The 74LS11 is a 3-input AND gate. So when the CPU wants to talk to one of
> the 3 ROMs, one of the inputs of the AND goes LOW, resulting in the output
> going LOW and activating the EPROM. Which part of the EPROM gets selected
> is also done by 2 of the _CS lines. You just need to put the 8 K BASIC and
> KERNAL and the 4 K char into the right parts of the EPROM. The 8 K block
> where A13 and A14 are both low stays empty.
>
>  Gerrit
>
>
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