Chapter 11.3: Headwinds -- Church
Chapter 11.4: Headwinds -- Buggy Floppy Controller
[JMR2020101528 -- My apologies for the change in format. Google's messing around with the editor.]
Monday, after classes, I spent a couple of hours in the lab testing low-level control operations for the disk drives. Jeff and Mark stuck around again to watch and talk, helping me stay focused.
Julia dropped by to see how things were going, and Jeff and Mark went over her notes with her again while I was deep down the rabbit hole. She stayed until I came up for air.
"Thanks for helping Julia with these notes, guys."
"No problem," Jeff shrugged. "I've been checking my own while we're at it."
"Me, too."
"Let me see what we have." They showed me their notes, and Julia looked over our shoulders as I studied the three sets of notes.
"Okay, I think I can see what we need to talk about next time we get everyone together. In the meantime, do you guys want to get a jump on everyone else?"
"As in?" Julia asked.
Jeff and Mark nodded.
"I have a couple of extra 68701s, if you guys want to get started wiring something."
"Yeah!"
"Hell yeah! Uh, sorry, Julia. Heck yeah."
Julia and I both rolled our eyes. I refrained from philosophizing about the real problem with so-called swear words.
"Won't they need to make schematics?" Julia asked.
I spent a half an hour helping Jeff and Mark work out full schematics for 6801 trainers, referring to my data sheets and application notes as we went, with Julia watching and somehow getting useful notes from our work. When we were done, we had enough to make parts lists for Mark's and Jeff's schematics, and I gave them both 68701s stuck into anti-static foam pads.
(Don't leave ICs in anti-static foam for more than a few months. It will do bad things to the leads, especially if you forget and leave them there for years.)
"I need to go back down the rabbit hole again."
"Can I copy your schematic?" Julia asked.
"Sure," I agreed without thinking too deeply as I turned back to the scopes and my source code.
"Can you guys help me make a parts list out of Joe's schematic?"
Dr. Brown came over to take a look.
"I do hope you guys aren't forgetting about mid-terms next week."
"No prob."
"On top of 'em."
I looked over at Julia.
"I'm fine. How about you?"
"I'm ahead of everything, too."
"Don't want any of your teachers complaining to me."
"Okay," I said. "We'll keep this short."
Julia, Mark, and Jeff worked out parts lists for each of the trainers as I dug back in.
At home, after delivering the newspapers, I studied what I had on the Shugart interface definition and the Western Digital interface commands for the 17XX series controllers, borrowing Giselle's computer to test my understanding.
Dad ducked in to see how things were going. I was struggling with timing problems I was having because BASIC was not fast enough, and I showed Dad how the program couldn't get back to the controller quickly enough to check results.
"What do you think you need?"
"Well, an ICE would be nice, but that's pretty expensive."
"Ice?"
"In-circuit emulator."
"Oh. And now I really know. Does it cost more than an Apple computer with all the needed options?"
"Yep. Especially since I'd need a decent scope and some other expensive tools to go with it. Something like double or triple what an Apple with the essential options would cost, at minimum, even if I were buying used test equipment."
"Well, we don't have the budget of a factory. Is there anything that would help that doesn't cost as much?"
"Uh, yeah. Radio Shack has an editor/assembler program called EDTASM that would allow me to write 6809 assembler code that would be fast enough."
"How much?"
I got out the Radio Shack catalog and showed it to him. "Maybe I should seriously consider buying this," I mused to myself.
Dad cocked his head. "It's only about the same as the disk version of the word processor cost. Maybe you should let me cover it." Then he pointed to a program cartridge with the same name. "This is cheaper, what is it?"
"It's a cartridge version of the same program."
"How much would it help?"
"Not much for the disk drives, at least without the MPI."
"MPI? What's that?"
I showed him the page where that was. "Multi-pak Interface. It allows you to use up to four cartridge paks at once -- game paks, program paks, I/O cartridges and whatnot."
"Now I remember Trina explaining that. Expandability is good. Would the MPI and the cartridge EDTASM help?"
"I'm not sure if they would help right now. No, probably not. If Radio Shack had used the 6809's 64K address space more carefully, so that using the cartridge version didn't require using the MPI to switch the floppy controller in and out of the memory map, maybe so. Or if the cartridge recognized the MPI and had provisions to work through it. It doesn't look like it does. So the switching back and forth is going to be a problem whose best solution is the disk version of the program anyway."
"Would Zed or your Mommy or I be able to use this?"
"I don't think so ..."
Giselle looked at me doubtfully, as if maybe I shouldn't decide such things for her.
"Well, it's pretty arcane ...," I tried to explain.
We continued to discuss my needs and Giselle's needs for another couple of minutes before I called Radio Shack to see if they had the disk version in stock. They did, and I rode my bike out to get a copy of the program, leaving unsettled the question of whether Dad would cover the cost if I needed the money later.
It turned out there was a sale, and I bought both the disk and cartridge versions for less than the catalog price of the disk version. Radio Shack was good for those sales.
When I got back, Julia had come over, and she joined us for dinner. After dinner, she waited and worked on homework while I went out to catch a few customers' late subscriptions.
When I got back, we talked while she worked on her homework and I used assembly language to write programs to investigate the Color Computer's disk drive controller and sketched out plans to implement a drive controller that presented a WD17XX compatible interface using a 68701 and some other parts instead of Western Digital's controller.
Denny called during the cheap time after Julia left.
"So Dad says she's a real beaut."
"Dang if she isn't."
"What about church?"
"We've talked a little about that, and we both seem to be okay with keeping things cool and keeping the question of religion open."
"Keep your spiritual eyes and ears open, and make sure she talks with the missionaries as soon as possible."
"Right. And I'll need to spend time with her pastor. We both need information."
"So, about the Micro Chroma 68 boards, I've got good news and bad."
"Give me the bad news first."
"My boss said that there are more Micro Chroma 68 main boards somewhere, but they aren't really enthusiastic about selling them to students. They'd rather the students get experience on the 6801 or 6805."
"Not the 6809?"
"They really don't seem all that anxious to have people using the 6809."
"No?"
"We'll have to talk about it sometime."
"Yeah?"
"Yeah. Sometime later."
"And the good news?"
"Good news is they are interested in sampling 4K EPROM versions of the 68705 to you and your classmates to use building trainers, if this is an official class."
"What are the students going to do for tools?"
"Motorola can make a cross-assembler available to you on disks that can be read under MDOS or Flex."
"Cross assembler I can run on the Micro Chroma to write code for the 68705s?"
"Yeah."
"Great! But what do they mean by official class? It's not in the school catalog. There apparently is some talk about making an official project class, but nothing solid, yet."
"Your teacher involved?"
"Yeah. He keeps an eye on us while we're in the lab. He's letting me lead the project, though. Twenty-some students want to build computers."
"Can somebody from our student liaison office get in contact with him?"
"I'm sure he'll agree to that. You don't think they might sample us 68701s if some of the students were doing a 68701 daughterboard conversion to the Micro Chroma 68, I suppose? Some of the students are interested in that."
"Good question. I'll ask."
I mentioned the interest from Motorola to Dr. Brown first thing when I saw him on Tuesday. He said he'd welcome contact from Motorola.
After classes, we were back in the lab, with professors and students dropping in to see what was happening while I was working in the electronics lab, then leaving when the interesting parts seemed to be too rare, or to end too quickly.
Mark and Jeff had 7-segment displays and other parts, so I showed them how to test their 68701s in single-chip mode. Then while I worked on the computer, they wired the test circuits. Julia watched as we worked, helping hold things when we needed a third or fifth hand.
After I ran some tests with my controller designs, Mark and Jeff were at a point where they could fully test their MPUs, so they got on the computer to burn some simple test programs into their 68701s' ROMs. The test programs were supposed to flash LEDs, but the results weren't what they expected.
So they used the scope to figure out why, with Julia again providing extra hands, holding scope probes and running commands on my computer. Pretty soon they had successfully tested the MPUs themselves, and went back to work on the wiring.
When I was done, the three of them listened to me explain what I was doing, and offered suggestions as I walked verbally through the program flow for the disk controller commands.
Mark and Jeff had made significant progress on their trainer boards by the time I was ready to leave.
Julia followed me in her car, and she studied while I folded and delivered newspapers. When I got back from throwing the route, I showed her how to strip the ends of wire-wrap wire and wrap it around the socket and component leads in point-to-point wiring, and how to wet the connections with solder.
Wire-wrap posts could have provided a more sure connection, but I was keeping my budget tight instead of buying wire-wrap sockets and a powered wrapper gun.
When she was confident of her work, we took turns wiring and checking. We got enough of the circuit done that I could program a 68701 with the code to test the seek command and watch the heads move over the spinning disk. Then we took an hour to work on her homework, reading her report drafts together and letting her practice explaining and defending her research approach.
"You know, I'm skipping Bible study class tonight."
I glanced at Julia. "It 's going on right now?"
"It just finished, I assume."
"Next week?"
"Every Tuesday."
"Let's plan to go together next week."
She smiled and nodded. "I'd like to. Do you guys have Bible study?"
"We call it Institute for adults, Seminary for teenagers."
"Seminary?"
"Not the seminary you're thinking of, just a one-hour class before school."
"Before school every day?"
"Yeah."
"That's dedication. Is, uhm, Institute every day, too?"
"Every Thursday, in Midland. I've been studying on my own, instead, fifteen minutes to an hour a day."
"Are you going to study today?"
"Yeah. You want to join me?"
"I think so. Sure."
"I'm working through Isaiah right now. Does that sound good?"
"Isaiah -- in the Bible?"
"Certain chapters of Isaiah are also in the Book of Mormon, and 'I'm studying them side-by-side."
"Isn't Isaiah hard to understand?"
"A few years ago, I had Boston cranked while I was reading the Isaiah 2 passage in the Book of Mormon."
"Boston?"
"Yeah, I know. Head-banger music. But it's not as raw as Van Halen."
She shrugged. "The name of groups?"
I had to laugh. "Sorry. I don't have any Van Halen. You want to listen to a little Boston on low volume?"
"I'm not sure."
I dug out Boston's eponymous album and put on "More Than a Feeling", volume low.
After about thirty seconds, she shook her head. "I don't think I hate it, but it doesn't really do anything for me."
I lifted the needle. "Probably just as well. Anyway, in the middle of that kind of storm, cranked, I heard the Holy Spirit."
"No way."
I dug out my Bible and Book of Mormon and opened the Bible to Isaiah 2 and the Book of Mormon to 2nd Nephi 12. I started with verse one in the Book of Mormon, reading out loud. She read along from the Bible, comparing the text as she went. Then she stopped me and read verse two out loud.
"What's this 'mountain of the Lord's house"?
"It's oversimplifying, but we think it means the temples."
She shook her head. "Okay, I'll ask more about that later. You take verse three."
I read, and she nodded. "I think I see what you mean about your temples. You did say that there is something you teach there, right?"
"Right. Take verse four?"
She read, stopping for thought at the plowshares and pruning hooks before finishing. "This is a favorite verse."
"Definitely."
"Is this where you heard the Spirit?"
"Yeah, but more to come." We alternated verses until I had read verse seven. "This is where I really started feeling the weight of the Spirit. Full of gold, no end to their treasures. Go ahead."
She read verse eight and then looked up at me. "Worship the works of their own hands?"
I nodded. "Yeah. Works of our own hands. I looked at my stereo when I read that and thought about what idols are. There's a lot of tiny bits of precious minerals, finely worked, in our electronics. And then I looked at an electronics project i was working on at the time. I think it was a sound generator of some sort."
"Gold?"
"Gold and rare earths, crystalline like jewels, if you look at it under a microscope. I'll show you that sometime."
"That would be interesting. But this next ...," she trailed off.
"Yeah," and I read verse nine. "Neither the mean man nor the great man will be humble. That's something we have to remember in all of this. Otherwise, the stuff we build with our own hands will condemn us before God." I nodded over at the computer.
She raised her eyebrows and breathed a deep sigh, then somewhat hesitantly continued with verse ten, and we traded verses until she read verse twenty-two.
"I guess the reason this chapter is repeated in the Book of Mormon is that God thought it was important?"
"Yeah. I think so."
"I see what you mean. I feel the witness of the Holy Spirit, too. But I think the devil is also whispering things in my ears."
"I stop to pray when that happens."
I reached for her hand, but she drew back.
"I need to do this myself."
We were both silent for a few minutes.
"Okay, I understand now. Thank you for showing it to me. This is important."
We talked a bit more, and she headed home.
Denny called again during the cheap hours.
"My boss asked if you were interested in designing a full Micro Chroma 6801 version. I told him I thought you were."
"Yeah, that's kind of in my plans."
"I'll tell him you said so. His boss is interested in watching what you demonstrate to the IBM people."
"Oh? I assume he won't be able to come on Thursday. What's he got in mind?"
"Motorola seems to be interested in having you do an internship with them, too."
"What have I gotten myself into?"
"Stress?"
"Feeling a little queasy. Too much happening too fast."
"If you'd done more merit badges in Scouts, you'd be more used to this kind of thing."
I let out a wry chuckle and a sigh. "There's something I can't argue with. Let me give you Dr. Brown's phone number to pass on to your boss." I read him the number from the school directory. "I'll check with him as soon as I see him in the morning."
"Okay, and let me give you the liaison office number, too."
I took it down.
"Julia helped me wire stuff today."
"Yeah?"
"Yeah. She's good with her hands."
"Hmm?"
"Soldering."
"Ah. Soldering. Good. Sounds interesting."
I shook my head at the phone. "Knock that off."
"Heh. You'll understand some day when you're married."
"That'll be soon enough."
"True."
"We also read 2nd Nephi 12 and Isaiah 2 together before she went home."
"She understood that?"
"Yep."
"Wonderful. Go get some sleep."
"Thanks. You, too."
After reading a few more verses in the New Testament, from Paul's discussion of avoiding eating food sacrificed to idols to avoid misleading people, for the first time in more than a month, I picked up Tera he and read myself to sleep. I did not stop to look any words up.
When I took the Micro Chroma 68 in to the lab Wednesday morning, Dr. Brown was waiting for me.
"I hope you won't mind."
"What?"
"Members of the school board and some of the professors want to observe what you demo to Ms. Bight tomorrow. I took the liberty of calling her after you left yesterday, and she said it would be great to watch you perform before an audience."
I laughed. "My brother says Motorola wants to watch, too."
"He called me, and so did Motorola's student liaison office."
"Oh." I blinked.
"They're sending somebody from their student liaison office tomorrow."
"Well, I guess we might as well have all the project group come in, too, so they can watch us discuss the project."
"Didn't I say? A project meeting is what they want to see most."
I sighed. "Then we'd better let everyone who came last week know."
"We can mention it in class today. I've let Professor Crane know, so he can tell your friends from the BASIC class. There are students in the microprocessors class who are interested, too. Mind if I invite them?"
"How many?"
"Five or so."
"I think five more won't force us to move things to the gym."
Dr. Brown laughed, and I joined him.
"Is this going to cause problems with teachers worried about mid-terms?"
He sighed and gave me a wry grin. "Prob'ly. But it's an opportunity that doesn't come around very often, so the guys upstairs have told me to go ahead with it."
Again, Julia, Jeff, and Mark worked with me after classes were done, and with their help, using the oscilloscope, I was able to get the seek command and the read and write track commands working enough to format a disk and test the format.
Jeff and Mark got their trainers wired in breaks from helping me, and wrote some simple test programs to burn into their ROMs. I didn't ask where they found their keypads.
"Where are the I/O versions of the unary instructions?" Jeff was looking at the 6800's datasheet, puzzled. He was typing his program in on the computer, and had gotten stuck.
"I/O? Those aren't 8080s, there are no I/O instructions."
Mark looked up, too. "But the binary instructions have the mode."
"You're talking about the direct page addressing mode?"
"Maybe so." Jeff checked the datasheet again. "Uhm, yeah."
"Bottom of the memory map. I guess the designers thought there was no room for the instructions. Nothing special to do, the assembler will just generate extended mode addresses for them."
"Isn't that going to be a problem?" Mark asked.
"It's all memory mapped on the 6800 series. Just takes a cycle longer. I'll admit, I think it would have been nice if Motorola had provided direct page mode op codes for the unary instructions, and brought out enough signals to separate direct page space from the rest of memory if one wanted to. That would have been way cool."
Jeff, Mark, and Julia all three looked at me blankly.
"Anyway, nothing to worry about. Just do it."
Neither Jeff nor Mark looked satisfied, but they returned to their programming.
Before I left, both of them had their trainers cycling through the segments on the 7-segment LEDs using the bit rotate instructions, using programs they had assembled by hand.
Julia didn't follow me home, but she dropped by again after I was done with the newspapers, and helped me get the sector read and write commands partially working, and then I helped her again with her homework.
Unfortunately, Giselle's Color Computer could not use the disk I formatted with the Micro Chroma 68, and my read and write sector routines would not work with a disk formatted on the Color Computer.
I spent some time checking my parity generation and testing, but it looked right, and didn't seem to be the cause of the problem. Julia got lost when I explained it to her, at least, she thought she did.
Giselle gave me permission to take the Color Computer to school the next day, telling me that she wanted to come and watch, too.
And she also joined us for scripture study before Julia left.
I called Denny.
"Help?"
"Heh. Break a leg tomorrow."
(Yeah. This is a pure flight of fantasy. But in order to have been able to start a second microcomputer revolution, I would have needed something like this to happen.)
[Second backup at https://joel-rees-economics.blogspot.com/2020/03/bk01-33209-headwinds-buggy-floppy-controller.html.
Original backup at https://joel-rees-economics.blogspot.com/2020/03/bk-33209-headwinds-buggy-floppy-controller.html.]
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