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Home » RBC Forums » General Discussion » Plasmo's 68k pathfinder projects (68K, 68000, 68020, 68030, 68040, 100mm x 100mm pc board)
Re: Plasmo's 68k pathfinder projects [message #4557 is a reply to message #4556] Wed, 11 April 2018 14:58 Go to previous messageGo to next message
kkeeley is currently offline  kkeeley
Messages: 26
Registered: July 2017
Location: Melbourne - Australia
Junior Member
Thanks for the suggestion on the XPLA3 family and Lattice ispMACH 4000V family, I'll have a look at these as well.

My main concern to start with was use a 3.3V CPLDs in a 5V environment, but it appears you have had success with this without the need for level shifters. So now I can focus more on what logic I require in the CPLD, this will then determine the final device size required, I'm hoping to keep to something that can be hand soldered, doesn't seam to be to many options in PLCC, but TQFP seams to offer a few more options, not too sure how difficult it will be to solder 0.5mm TQFP by hand but I've seen that it can be done. Looking at the pricing they all seam to be about the same, give or take a few bucks. The real difference is the tools/software required to use them, for this so far I'm leaning towards the Xilinx's or Lattice devices at the moment.

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Re: Plasmo's 68k pathfinder projects [message #4558 is a reply to message #4557] Wed, 11 April 2018 17:49 Go to previous messageGo to next message
wsm is currently offline  wsm
Messages: 226
Registered: February 2017
Location: AB, Canada
Senior Member
The XCR3032/64XL and XC9536/72XL were available in 44 pin PLCCs but these tend to be very I/O pin limited (36 & 34 respectively).

I've been hand soldering the 0.5mm 100VQFP, 144TQFP & 208PQFP packages without much of a problem. The step down to 0.4mm is about my limit and I find them MUCH harder. I use an old Weller WTCPN iron with PTS7 tips (0.4mm) plus .015" / .37mm Multicore solder and LOTS of flux (Kester 952D6 or 951 in pens). Be sure to very carefully position the part before soldering and only use a LITTLE bit of solder. Originally I used to create a few bridges on 0.5mm parts that needed to be wicked but now I can usually do one of these without any bridges.

I found ispLEVER to be MUCH faster than ISE but the version I used had a few nasty bugs that might have been fixed by now. If using ABEL, there are slight differences in how they interpret ranged variables which may require some coding changes. At the end of the day, they both can work so I select the device as my main criteria. I haven't actually used Altera's tools so I can't comment on them.

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Re: Plasmo's 68k pathfinder projects [message #4559 is a reply to message #4558] Wed, 11 April 2018 18:33 Go to previous messageGo to next message
kkeeley is currently offline  kkeeley
Messages: 26
Registered: July 2017
Location: Melbourne - Australia
Junior Member
Thanks

This is all very useful information, do you know if ispLEVER supports the ICE40 fpga's or would I need IceCube for them? I've seen a few designs for VGA and SDR Memory controllers that use the ICE40 fpga's. I'd like to reduce the number of tools to learn/use to a minimum. I think that Xilinx supports the XC9500XL, XPLA3, Spartan 3E and Spartan 6 families all in the one version of ISE (14.7 I think).

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Re: Plasmo's 68k pathfinder projects [message #4560 is a reply to message #4559] Wed, 11 April 2018 19:06 Go to previous messageGo to next message
wsm is currently offline  wsm
Messages: 226
Registered: February 2017
Location: AB, Canada
Senior Member
ispLEVER supports the ispMACH devices but NOT the ICE40 ... for that you'd need IceCube.

ISE does support the multiple families *BUT* if you want to use ABEL rather than VHDL or Verilog you'll need a downlevel version.

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Re: Plasmo's 68k pathfinder projects [message #4561 is a reply to message #4560] Wed, 11 April 2018 19:31 Go to previous messageGo to next message
plasmo is currently offline  plasmo
Messages: 881
Registered: March 2017
Location: New Mexico, USA
Senior Member
Good discussion of Xilinx CPLD product lines. When Xilinx acquired Philips CoolRunner product lines, they had really strengthen their holds on the low-power CPLD. Altera supposed to have very user friendly tools, their schematic capture program was way ahead of its time, but these are 15-20 years old opinions. I don't know what improvements Altera (Intel) and Xilinx have made since. Since the products under discussion are 20+ years old, I suppose the capabilities of the tools at that time is still applicable today. Ultimately these tools have their strength & weakness and it is what you are used to that's important. I've used Altera since their early days with EP300/600/900 (mid 1980's) so it is unlikely I'll change tools.

I think it is worth the effort to learn how to solder SMT down to 0.5mm. It gives you much greater design choices and you can do so much with the low cost 10cm * 10cm pc board if you've mastered the SMT soldering process. I'm retired, so I'm not a spring chicken anymore, but with the help of stereo inspection microscope, fine soldering tip, 0.010 multi-core solder, and lots of flux, I still can do 0.5mm pitch without much of a mess. EPM7128SQC100 at 0.65mm pitch is downright easy.

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Re: Plasmo's 68k pathfinder projects [message #4563 is a reply to message #2193] Thu, 12 April 2018 09:42 Go to previous messageGo to next message
wsm is currently offline  wsm
Messages: 226
Registered: February 2017
Location: AB, Canada
Senior Member
Ken: I forgot to mention another possible CPLD that is available in 84-pin PLCC form and can run on 5V. Namely the Atmel (Microchip) ATF1508AS. They have quite a high Idd requirement and I haven't actually used them. Some of the newer S100computers boards use them.

Plasmo: I agree that we tend to get used to various tools and figure out their ideosyncrasies then tend to stick with them. I started using CPLDs with the Philips XPLA3 series but have looked at using several different families. Once I started using various 3.3V devices, the CoolRunner-II family added some useful features and a lower cost. I'm just starting to play with FPGAs but I still like the simple deterministic nature of CPLDs. However, features like dual-ported FIFOs plus LOTS of logic have swayed me to start playing with FPGAs.

Likewise, I've also got grey hair and still use a lot of OLD tools that I'm familiar with. That avoids one of the problems I foresee with the cloud and/or subscription model that a lot of tools are moving towards. For example, I still have PLD software and a programmer that is several decades old but I can still use it today to reproduce or update old designs, albeit on an older DOS machine that I saved.

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Re: Plasmo's 68k pathfinder projects [message #4604 is a reply to message #4563] Wed, 18 April 2018 12:28 Go to previous messageGo to next message
ale500 is currently offline  ale500
Messages: 44
Registered: April 2018
Member
I've been reading the forums for a while and just recently decided to join.

I did some 68k projects in the past (68008 with TTL glue, 68EC020 with XC9536) and I picked another project just a few weeks ago:
A 68SEC000 plus a Spartan6 (18 € board from aliexpress).

The 68SEC000 is great because it works with 3.3 V. I connected all processor pins to the FPGA (even MODE & A0... a waste) and did some minimum of glue in VHDL.
I implemented an 80x25 Text driver with font and 4 K Video RAM that seems to work ok.
The FPGA board has 32 MB SDRAM, bringing that up is my next step.

Here a couple of photos of the... setup.

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Re: Plasmo's 68k pathfinder projects [message #4606 is a reply to message #4604] Wed, 18 April 2018 20:39 Go to previous messageGo to next message
plasmo is currently offline  plasmo
Messages: 881
Registered: March 2017
Location: New Mexico, USA
Senior Member
Very nice! Too bad most retro CPU are 5V but 68SEC000 is one of the few exceptions. At 3.3V you have so much better selections of logic & memories. With a modern FPGA you can do just about anything you want. Add a SD card interface and you can have CP/M-68K. If you like the 68K family, there are 3.3V version of 68040 and 68060 is 3.3V. It should be fun to play with the high-end 68K processors.

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Re: Plasmo's 68k pathfinder projects [message #4609 is a reply to message #2193] Thu, 19 April 2018 00:55 Go to previous messageGo to next message
ale500 is currently offline  ale500
Messages: 44
Registered: April 2018
Member
That is also the plan, a SD card and a PS/2 keyboard.

The 68040 is also one of my targets, I did a board for it a few years ago, it has a 5 V-tolerant FPGA, a SpartanII (not E). The spartanII works, but I didn't got to test the 68040. There is something with the BUS frequency that is not clear. I think here is the right place to ask... I have a 25 MHz version, should I feed it with 50 or 25 MHz ?

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Re: Plasmo's 68k pathfinder projects [message #4610 is a reply to message #4609] Thu, 19 April 2018 05:34 Go to previous messageGo to next message
plasmo is currently offline  plasmo
Messages: 881
Registered: March 2017
Location: New Mexico, USA
Senior Member
68040 needs both clock and 2xclock. The relationship of the two clocks are tight as well as the rise & fall time. The MC88915 was specifically made to support the 68040 clocks. I think the modern FPGA's PLL should be able to duplicate the timing requirements of the 68040 clocks. Don't know for sure, never designed 68040 with the modern FPGA. I did design a 68060 prototype closely coupled to an Altera Stratix FPGA when Altera introduced their Stratix product and Parallax produced a low-cost (I think it was $125, but that was low cost at the time) Stratix BGA-to-WW-headers board. It never went to production and that was my last 680x0 project.

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Re: Plasmo's 68k pathfinder projects [message #7739 is a reply to message #4610] Sun, 31 May 2020 10:10 Go to previous messageGo to next message
newjes250 is currently offline  newjes250
Messages: 13
Registered: May 2020
Junior Member
To: Plasmo

I bought one of your Tiny68K assembled boards - and would like to use it as a TestBed to
see if I can replace the 68000 with a plugin board having a 68020 processor. Would you
know if such an upgrade in processors could be transparent and therefore compatible?
I believe 3 things could be changed if needed: the CPLD, a selectable serial EEPROM, and
the 68020 board. Why would someone want to do this? I have a 16Mhz 68000 system which is
begging for a upgrade of this type, and the Tiny68K could be used to discover the areas where
either timings or other issues might require changes. In fact I thought a TerribleFire PCB
with its 68020 (which I have) could be modified to act as the plugin pcb.

Any thoughts from you would be most welcome,
I have enjoyed very much using the Tiny68K.

newjes250

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Re: Plasmo's 68k pathfinder projects [message #7740 is a reply to message #7739] Mon, 01 June 2020 07:00 Go to previous messageGo to next message
plasmo is currently offline  plasmo
Messages: 881
Registered: March 2017
Location: New Mexico, USA
Senior Member
newjes250,
I think it is possible to plug a 68020 carrier board into 68000 socket with some signal translation. The problem is you may not see much performance improvement because the clock frequency is still 16 MHz and bus width is still 16-bit. Instruction cycle is reduced from 4 clocks of 68000 to 3 clocks of 68020, but you may need to add wait state to make up for the slower access time of 68000.

If you want to explore 68020 instructions, it is fairly easy to prototype a 68020 because of its dynamic bus sizing feature. https://www.retrobrewcomputers.org/doku.php?id=builderpages: plasmo:tiny020prototype I also have blank pc board of 68020 that I can mail to you free. https://www.retrobrewcomputers.org/doku.php?id=builderpages: plasmo:tiny020pcb

I haven't talked about it here, but there is a page on retrobrew wiki describing a recent 68020 design, MB020. https://www.retrobrewcomputers.org/doku.php?id=builderpages: plasmo:mb020 Which has 32-bit data bus and faster clock to fully use the 68020 capabilities. This design is also called frankenstein020 because it is collection of left-over RC2014 boards and whatever SIMM72 modules that's available.

Bill

[Updated on: Mon, 01 June 2020 07:01]

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Re: Plasmo's 68k pathfinder projects [message #7742 is a reply to message #7740] Mon, 01 June 2020 16:05 Go to previous messageGo to next message
newjes250 is currently offline  newjes250
Messages: 13
Registered: May 2020
Junior Member
To Plasmo:

I looked at the Frankenstein020, and you know it is closer to what my 16Mhz 68000 system needs to be for a real bump up in
performance. The photo of the motherboard with RC2014 cards shows a 20Mhz 68020 and a 22Mhz oscillator, although the schematic
lists a 16Mhz clock. I am wondering how close the RC2014 bus is to a PCXT bus which my system has: it uses regular XT cards for
HD MFM drive, Paradise VGA video card in 8bit mode, etc. Is the MB020 board still available? I have other XT and AT bus slot boards
that I could possibly couple to the RC2014 bus. The swap register feature would get the dram at address zero and up, which would
match as well.

Thanks so much for your response,

newjes250

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Re: Plasmo's 68k pathfinder projects [message #7744 is a reply to message #7742] Tue, 02 June 2020 20:46 Go to previous messageGo to next message
newjes250 is currently offline  newjes250
Messages: 13
Registered: May 2020
Junior Member
To Plasmo:

Now that I have viewed your MB030 design, the effort to using a 68020 is about the same as a 68030 design if I follow your current
CB030 project. Could I get a blank CB030 PCB with programmed/installed CPLD from you? The enjoyment of finishing the build with
my own components would be welcome.

Thank you for such wonderful designs.

newjes250

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Re: Plasmo's 68k pathfinder projects [message #7745 is a reply to message #7744] Wed, 03 June 2020 05:22 Go to previous message
plasmo is currently offline  plasmo
Messages: 881
Registered: March 2017
Location: New Mexico, USA
Senior Member
If you are in USA, I'll ship you a blank board free. With CPLD installed and programmed, CB030 or MB020 are the same price, $15 + $5 shipping in USA.
Bill
Edit, I have been preoccupied with other projects. I'll update the board inventory on the retrobrew wiki page to include CB030. Quick summary: partially populated with CPLD, $15; full kit with CPLD installed, $55; assembled and tested, $75. Ship to USA only $5 shipping <-- shipping internationally is ridiculously long due to COVID19.

[Updated on: Wed, 03 June 2020 05:29]

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