OT - limitation of PC's parallel port (was: Logic analyzer)

From: Spiro Trikaliotis (trik-news_at_gmx.de)
Date: 2002-04-18 08:01:03

  • Next message: Gideon Zweijtzer: "RE: 65GS10"
    Hello,
    
    "Gideon Zweijtzer" <gideonz@dds.nl> wrote:
    
    > I once made a simple 'logic analyzer' that monitors 16 pins and runs at
    > maximum of 40 or 50 MHz, so you have 25 or 20 ns resolution. What I did was
    > checking for changes of the signal levels and only storing the changes
    > together with a 16-bit timestamp, using a non-linear timer (the longer it
    
    That's exactly what I did with the PC, except that I used a linear timer 
    and did not use any external logic. This analyzer is even mentioned in my
    diploma thesis.
    
    A little bit OT, but someone here might have an answer, and as it might
    help in analyzing CBM hardware: ;)
    
    Does anyone know what is the (most) limitating factor when using the PC's 
    parallel port? Is it the usage of I/O address space, or the usage of the 
    ISA bus? I could obtain a PCI card for testing, but I don't want to spend 
    so much money (these are really expensive!) if I don't know if this makes 
    a significant change.
    
    I know that the CPU spends much wait states when using I/O address space,
    as it does when using something on the (internal) ISA bus. Which one is
    more limiting? Does anyone know if the parallel ports on external PCI cards
    use I/O or memory address space? I did not find any specifications on this.
    
    Anyone?
    
    Thanks in advance,
       Spiro.
    
    
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