Re: C= IC's (3)

From: William Levak (wlevak_at_cyberspace.org)
Date: 2000-12-07 09:28:42

On Wed, 6 Dec 100 g.baltissen@hccnet.nl wrote:

> Then the discussion about the 6530. Somebody said that he wanted some 901885's 
> to replace his 6530's. (Sorry, but I throwed away some mail which I stored in 
> the wrong directory so I forgot the name). Yesterday evening I found a chip 
> only marked 6530. And this reminded me of something described on my site i 
> 6530.htm. The 6530 is a custom chip with I/O, RAM and ROM. But addressrange of 
> the I/O and RAM could be customized as well !!! Take the KIM: it has 2 6530's 
> and both CS1 chipselects are connected to K5. And yet the I/O "knows" to which 
> address it belongs. This is made possible by factory internal masking. This 
> simply means that, even in case you don't need the onboard ROM, you cannot 
> replace one 6530 with another. (unless their masking is the same of course)

According to the data sheet,  not only CS0 and CS1 are mask programmable,
but also PB5 and PB6, making 4 mask programmable select lines.  When PB5
and PB6 are used as select lines, they cannot be used as interface lines,
so there is another incompatibility.

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