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85 lines
4.9 KiB
Plaintext
85 lines
4.9 KiB
Plaintext
Episode: 2137
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Title: HPR2137: Pause All The Things, Sega Genesis
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Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2137/hpr2137.mp3
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Transcribed: 2025-10-18 14:47:17
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---
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This is HPR episode 2,137 entitled, for all the things, Sega Genesis, it is hosted by
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SIGFLOPS and in about 6 minutes long, the summary is, learn how to create a hard
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weapon which for the Sega Genesis.
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This episode of HPR is brought to you by an Honesthost.com.
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Get 15% discount on all shared hosting with the offer code HPR15, that's HPR15.
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Better web hosting that's Honest and Fair, at An Honesthost.com.
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Hello everybody, this is SIGFLOPS and I will also notice the summary assembly and you're
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listening to Hacker Public Radio.
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This is going to be a real short one.
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It's going to be about making a hardware pause switch for your Sega Genesis or a Mega Drive.
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So what that is is the thing that we're going to do here is we're going to make a switch
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that pauses the clock of the processors, both the Z80 and the 68000.
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So I'll tell you just pretty much directly how that works.
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This is going to be like a 50 minute, 50 second HPR piece.
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So what I did was I've done a number of things, all of them didn't work.
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I actually ended up blowing out one Sega.
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I tried grounding certain things on the cartridge slot, like the data knowledge, the clock
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itself, grounding the clock itself kind of works, but it corrupts.
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And I suspect it corrupts because both you're passing the clock made instruction a lot
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of the time.
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And the registers, the internal registers of the 68000 processor are DRAM and get refreshed.
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And so there's no clock there, they don't get refreshed and things become corrupted.
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And so I looked at the pin out of the 68k and talked about it on Poit, this demo-seeing
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group and someone was like, yeah, assert the bus request, then wait for a bus grant.
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And then you have the bus to alter yourself.
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So I misunderstood exactly what they said.
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So I end up sending a bivolt to the bus grant, but that works beautifully.
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It's not a bus request, wait for a bus grant or anything like that.
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So yeah, just asserting bivolt to the bus grant pin on the 68000 processor, it's pretty
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good.
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I'm giving you some show notes here, let's see here, the top right is the big chip.
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If you have a Sega Genesis model one, the earlier versions, the 68k processor comes
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in this package.
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And what you want to do is be mindful of pin 11, which is bus grant inverse.
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That is, it's active low.
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If you have a newer Sega Genesis like an M2, it's the 11th pin as well with the same
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meaning.
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What you do is you assert five volts to it.
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And this is the tricky part.
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I end up destroying one Sega, because current goes the other way, because the bus grant
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is being asserted when we do DMA transfers and stuff like that, I assume.
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It gets grounded out by the switch.
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My switch has a little ground to it, which is an unusual switch to have.
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But feeling a better switch, what I did was I put a diode between the switches output
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and the bus grant pin.
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And that way, current goes from the switch to the bus grant and does not go the opposite
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way.
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And that works beautifully.
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So let me demonstrate it for you.
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I have a Sonic the Hedgehog, I'll pause here.
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So I pause it again, you can I'm pause it and pause it.
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And why don't we wait until the beginning care and I'll just keep on doing that.
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So it's, it passes the Z80 as well as the 68000.
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It does not pause the clock to the BDP, the graphics chip, which is good.
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So what I want to do in the future is make a button that advances a frame.
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And to do that, I need a microcontroller, a microcontroller to watch the horizontal sink
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and perform an on pause for the duration of that vertical trace.
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And so yeah, I'm I'm looking at some I'm looking at some at Mel mega, I'm sorry, at Mel
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tiny microcontrollers to use that.
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So next episode, I'm going to that's going to be about the pause button or the pause switch
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for the Sega Genesis.
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Hopefully I will have worked out a frame advance button as well.
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Thank you for listening everyone.
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This one is kind of off the cop so no editing, I don't like editing, it's pretty boring.
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So take care and enjoy the show notes and hack your Sega Genesis like there's no tomorrow.
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Bye bye.
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You've been listening to Hacker Public Radio at Hacker Public Radio dot org.
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We are a community podcast network that releases shows every weekday, Monday through Friday.
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Today's show, like all our shows, was contributed by an HBR listener like yourself.
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If you ever thought of recording a podcast, then click on our contributing to find out
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how easy it really is.
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Hacker Public Radio was founded by the digital dog pound and the infonomicum computer club.
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And it's part of the binary revolution at binrev.com.
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If you have comments on today's show, please email the host directly, leave a comment on
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the website or record a follow-up episode yourself.
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Unless otherwise stated, today's show is released on the creative comments, attribution,
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share a light 3.0 license.
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