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JackAsser
Registered: Jun 2002
Posts: 1994 |
NMI delay
How much is an NMI delayed if triggered during IRQ-setup? |
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... 45 posts hidden. Click here to view all posts....
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Krill
Registered: Apr 2002
Posts: 2854 |
Quoting Martin PiperTo really get an answer to this the PLA ROM needs to be understood. Please don't call it PLA. It's not programmable, it's just a ROM. =) |
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JackAsser
Registered: Jun 2002
Posts: 1994 |
Quote: Quoting Martin PiperTo really get an answer to this the PLA ROM needs to be understood. Please don't call it PLA. It's not programmable, it's just a ROM. =)
The LA. :) |
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Krill
Registered: Apr 2002
Posts: 2854 |
Quoting JackAsserThe LA. :) Lookup array. Basically table. =) |
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Martin Piper
Registered: Nov 2007
Posts: 645 |
Quote: Quoting Martin PiperTo really get an answer to this the PLA ROM needs to be understood. Please don't call it PLA. It's not programmable, it's just a ROM. =)
"it's actually a PLA"
https://retrocomputing.stackexchange.com/questions/15227/why-di.. |
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Krill
Registered: Apr 2002
Posts: 2854 |
Quoting Martin Piper"it's actually a PLA"
https://retrocomputing.stackexchange.com/questions/15227/why-di.. So, well, it's programmable (by whoever edits a mask and re-runs production), but not field programmable... essentially the same technology as ROM. Ooookay. :)
Easy counter: https://electronics.stackexchange.com/questions/5825/what-is-th.. =) |
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Martin Piper
Registered: Nov 2007
Posts: 645 |
https://en.wikipedia.org/wiki/Programmable_logic_array
"the original 6502 chip contained a PLA"
It's obviously not a full ROM. |
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chatGPZ
Registered: Dec 2001
Posts: 11147 |
That's simply wrong. It's a decode ROM, no more, no less. (And yes, what Krill said. Its not a traditional ROM, sure. Its a logic array. And that kind of thing is usually called decode ROM - not PLA. PLA is programmable, not mask edited.) |
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Martin Piper
Registered: Nov 2007
Posts: 645 |
Quote: That's simply wrong. It's a decode ROM, no more, no less. (And yes, what Krill said. Its not a traditional ROM, sure. Its a logic array. And that kind of thing is usually called decode ROM - not PLA. PLA is programmable, not mask edited.)
Wrong. The PLA in the 6502 is sparse. A full ROM maps every single output. The 6502 PLA saves space compared to a full ROM.
It's why we have illegal opcodes.
https://www.pagetable.com/?p=39 |
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chatGPZ
Registered: Dec 2001
Posts: 11147 |
You don't have to copypaste me the ill informed stuff that you found on reddit.
FPLA is a synonym for the (modern) FPGA btw - and has zero to do with the oldschool "PLA".
(yes, please inform me about how illegal opcodes work, i always wanted to know) |
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Martin Piper
Registered: Nov 2007
Posts: 645 |
Quote: You don't have to copypaste me the ill informed stuff that you found on reddit.
FPLA is a synonym for the (modern) FPGA btw - and has zero to do with the oldschool "PLA".
(yes, please inform me about how illegal opcodes work, i always wanted to know)
Wrong again.
Look at the chip layout, it's obviously a PLA, not a full ROM.
http://www.visual6502.org/JSSim/expert.html?nosim=t&panx=110.5&.. |
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