Date   : Fri, 20 Mar 2009 09:17:01 +0000
From   : splodge@... (Richard Gellman)
Subject: Hardware questions

Hi,

Many thanks for all the replies to clear this one up. The device I'm
building *may* generate interrupts, so I'll make sure there's a
disable-on-reset circuit involved somewhere to stop them from causing any
peculiarities on startup.

On a related note, do any of the techier electronics gurus here know of a
(cheap) simple USB device that would give high speed (~ 2Mhz) access to a
range of bidirectional i/o lines using API/DLL calls from Windows?

Thanks

-- Richard


On Fri, 20 Mar 2009 00:32:01 -0000, "Mark Haysman"
<jumbos.bazzar@...> wrote:
>> "Mark Haysman" wrote:
>>> > During the startup sequence it zeros the IRQ-copy-of-A with
interrupts
>>> > disabled and briefly reenables them. If IRQ-copy-of-A is corrupted it
>>>
>>> So, can you not just blindly put  64K of SRAM with A8-15 controlled by
a
>>> latch from FCFF, and the lower address and data bus connected to simply

>>> give
>>
>> Yes.
>>
>>> you 64K of extra paged RAM? Will having RAM at FDFE and FDFF confuse
the
>>>
>>> OS?
>>
>> No, because the "test hardware" has to assert IRQ after RESET to
>> generate an interupt and cause the IRQ-copy-of-A to be corrupted.
> 
> Nice, I had always thought that was the case, but reading that about the 
> test hardware got me worried for a moment!
> 
> It's also useful to note that you can make the OS jump to code that's
paged
> 
> in at FDxx if you wanted to...do all versions of the OS do that?
> 
> Mark. 
> 
> 
> 
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