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Update @ Charles MacDonald's: Deco Cassettes (Feb.5)
#275349 - 02/06/12 05:06 PM
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Re: Update @ Charles MacDonald's: Deco Cassettes (Feb.5)
[Re: Smitdogg]
#275364 - 02/06/12 09:03 PM
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Interesting!
I have a question though...
Quote:
Writing to the data register or command register will tristate the data bus, causing the 8041 to latch an open-bus value.
I have never heard of "tristate" being used in this context... what does it mean?
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| R. Belmont |
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Cuckoo for IGAvania
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Reged: 09/21/03
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Re: Update @ Charles MacDonald's: Deco Cassettes (Feb.5)
[Re: apeman]
#275368 - 02/06/12 09:58 PM
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> I have never heard of "tristate" being used in this context... what does it mean?
It means that a given device is completely disconnecting itself from the bus, leaving the bus to "float" to random garbage values and/or be driven by some other device.
This is the origin of the "open bus read" commonly encountered in 8-bit computers; if you try to read an address where no device is mapped, *everything* goes tristate and the CPU reads back a semi-random value.
Edited by R. Belmont (02/06/12 09:59 PM)
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Re: Update @ Charles MacDonald's: Deco Cassettes (Feb.5)
[Re: R. Belmont]
#275418 - 02/07/12 07:54 AM
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> It means that a given device is completely disconnecting itself from the bus, leaving
> the bus to "float" to random garbage values and/or be driven by some other device.
Thank you Sir! It's been ages since my electronics lectures at uni...
If anyone's interested, there's a Wikipedia article on it.
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