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Re: Z80 Multi Board Computer [message #9073 is a reply to message #9072]

Tue, 31 August 2021 07:58

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi Edzard,
As patches go, that looks pretty good!

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9074 is a reply to message #9073]

Tue, 31 August 2021 08:59

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 VDC

/forum/index.php?t=getfile&id=2401&private=0

Video board for Z80 MBC using MOS 8568. Note: this board uses dot clock of 16 MHz or less meaning almost all VGA monitors will not sync with it. Instead use a CGA/EGA scan converter to VGA (eBay, Amazon)

Thanks, Andrew Lynch

PS, please review the schematic and PCB layout and let me know if you find any problems or suggest changes. I would like to find the problems before going to manufacture PCB so you help will be greatly appreciated

update: posted new design files to capture latest updates.

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[Updated on: Fri, 03 September 2021 07:16]

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Re: Z80 Multi Board Computer [message #9076 is a reply to message #8396]

Tue, 31 August 2021 15:50

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 Prototyping V2

/forum/index.php?t=getfile&id=2385&private=0

This PCB addresses IC spacing error on previous version of Z80 prototyping board

update: added Gerber files for PCB manufacturing

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[Updated on: Tue, 09 November 2021 07:56]

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Re: Z80 Multi Board Computer [message #9095 is a reply to message #8396]

Fri, 03 September 2021 07:19

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 KBDMSE

/forum/index.php?t=getfile&id=2402&private=0

This is the Z80 keyboard and mouse board intended as a companion to the Z80 VDC board. Together these two boards serve as a terminal replacement so the Z80 MBC can be more self-sufficient.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9097 is a reply to message #8396]

Fri, 03 September 2021 08:35

edzard
Messages: 64
Registered: August 2019

Member

Hello Andrew,

Nice and impressive work!

Would you think it's feasible/possible to port the ParPorProp to the MBC-system?
Maybe without the serial port?

Best regards,

Edzard

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Re: Z80 Multi Board Computer [message #9098 is a reply to message #9097]

Fri, 03 September 2021 13:34

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi Edzard,

Most likely but I would like to see the circuit to verify if it can fit on the Z80 MBC board. Since it is 100x100mm things can get pretty tight. Let me check

Does it matter ParPortProp or PropIO V2? They both look pretty similar

Thanks, Andrew Lynch

PS, why no serial port?

[Updated on: Fri, 03 September 2021 13:43]

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Re: Z80 Multi Board Computer [message #9099 is a reply to message #9098]

Sat, 04 September 2021 02:21

edzard
Messages: 64
Registered: August 2019

Member

Hello Andrew,

lynchaj wrote on Fri, 03 September 2021 13:34

Hi Edzard,

Most likely but I would like to see the circuit to verify if it can fit on the Z80 MBC board. Since it is 100x100mm things can get pretty tight. Let me check

Does it matter ParPortProp or PropIO V2? They both look pretty similar

Thanks, Andrew Lynch

PS, why no serial port?

I thinks there's not much difference other then the footprint (so it can fit easily on the Zeta V2)?

With regards to the serial port: I was just thinking about the space. We already have a serial port and maybe that way some PCB space could be re-used.
The advantage of the ParportProp for the MCB system is that we get a VGA/Keyboard solution with available parts.

Or if we only want the VGA/keyboard solution (no serial/CF card) the VGA Serial Terminal for the RC2014 is maybe also a possibility.
https:// www.tindie.com/products/maccasoft/vga-serial-terminal-pcb-fo r-rc2014/

Best regards,

Edzard

[Updated on: Sat, 04 September 2021 02:21]

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Re: Z80 Multi Board Computer [message #9114 is a reply to message #9099]

Wed, 08 September 2021 05:21

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
During the recent builds of the respin PCBs a couple of issues came up on the Z80 RAM V2 and Z80 Serial V2 boards that I think need to be addressed. These are not show stopper bugs but are more quality-of-life type issues. They can be worked around easily enough but are a real pain to find and deal with so I am going to go ahead and respin these boards.

For the RAM board the issue is the DS1210s and power supply sag tolerance. Right now the tolerance is set to the 5% and it can be overly sensitive in some situations. I am going to add a jumper to allow selection of either the 5% or 10% power supply tolerance depending on your needs. Since builders use a wide variety of power supplies this can be very handy and help explain eliminate some mysterious failure-to-start errors and hang ups. Not something you'd notice right away but it definitely came out in the test builds so I think this needs to be fixed before moving on.

Regarding the Serial board, it turns out there is an essential feature we are going to need eventually (Automatic Flow Control) which hardly any of the ACE UARTs in DIP-40 support. So I am going to add a PLCC-44 socket to enable usage of 16C550FN type UARTs in addition to the classic DIP-40 UARTs. One or the other but not both. AFC is much more common in the PLCC-44 UARTs. At present it seems there is only a single DIP-40 ACE UART that supports AFC and that's the SC16C650BIN40 from UTsource. It's not that the old style 16550 UARTs won't work but they don't have AFC and that's going to be a real bummer sooner or later. So far, we've been using relatively low speed data rates on the Z80 MBC (38400 bps and lower) but to reach higher rates the AFC is going to be highly desirable. Not absolutely required but it makes things much easier and generally less of a disappointment.

So that's the situation, if you have any other ideas or proposed changes/enhancements to the Z80 RAM V3 and/or Z80 Serial V3 board let me know and/or reply to this thread. All are welcome.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9116 is a reply to message #9114]

Wed, 08 September 2021 15:19

b1ackmai1er
Messages: 396
Registered: November 2017

Senior Member

Hi Andrew,

For V3 serial consider adding anti latch up circuit to cater for fake max232's

https://www.retrobrewcomputers.org/forum/index.php?t=msg& ;th=623&goto=9007&#msg_9007

Regards Phil.

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Re: Z80 Multi Board Computer [message #9117 is a reply to message #9116]

Wed, 08 September 2021 17:17

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi Phil
Is this the couple extra schottky diodes like in this schematic or is there more to it?

https://cdn.hackaday.io/files/1680147188310976/A260719%20-%2 0SCH.pdf

Thanks, Andrew Lynch

PS, after a lot of searching around on this topic and seeing many possible solutions, the one below seems to give a good explanation and solution. See the AN218 linked Exar datasheet

https://electronics.stackexchange.com/questions/122769/max32 32-overheating-burnt-after-connecting-to-pc/426675#426675

[Updated on: Thu, 09 September 2021 04:31]

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Re: Z80 Multi Board Computer [message #9118 is a reply to message #9117]

Fri, 10 September 2021 02:25

b1ackmai1er
Messages: 396
Registered: November 2017

Senior Member

Sorry Andrew, I am not familiar with the circuit or how it works.

I don't even know what "latch-up" is lol

Edit: I read the app note and get the idea now but cant say I understand it Smile

[Updated on: Fri, 10 September 2021 02:38]

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Re: Z80 Multi Board Computer [message #9130 is a reply to message #8396]

Thu, 16 September 2021 16:34

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
Z80 DMA is built and started testing. Here is an early copy of the DMA monitor program called DMAmon used to verify DMA operation.

This is an early copy and does not fully work yet. Still in development

Thanks, Andrew Lynch

Attachment: DMAMON02.zip
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Re: Z80 Multi Board Computer [message #9139 is a reply to message #9130]

Mon, 20 September 2021 09:14

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
The Z80 processor V2 and Z80 RAM V2 boards have been tested and seem to be working fine. Found a couple of issues during build and test so I am going to do respins of these boards mainly because they are so fundamental to the MBC they have to work right the first time or will cause endless grief.

If you are interested in building your own Z80 MBC system please let me know or you can just have your own PCBs made using the posted Gerber files and your favorite PCB manufacturer like JLCPCB. There is a small team building the Z80 MBCs and it is a lot of fun plus interesting challenges. It's what makes this a great hobby!

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9142 is a reply to message #9139]

Tue, 21 September 2021 06:53

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 RAM V3

/forum/index.php?t=getfile&id=2412&private=0

PCB respin to address minor findings from build and test. Adds 5% or 10% tolerance jumper to DS1210s to improve power supply sag performance (was 5% only)

update: added Gerber files

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[Updated on: Wed, 22 September 2021 05:53]

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Re: Z80 Multi Board Computer [message #9143 is a reply to message #9142]

Tue, 21 September 2021 06:56

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 processor V3

/forum/index.php?t=getfile&id=2416&private=0

PCB respin to address minor findings during build and test. Fixes IM2 interrupt circuit and eliminates work around procedure. Makes IM2 circuit only respond to interrupts it receives as to not interfere with other sources of interrupt vectors/op codes from the bus. Also allows interrupt vectors/op codes through to the CPU data bus instead of blocking them.

Update: added Gerber files

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[Updated on: Tue, 25 January 2022 09:02]

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Re: Z80 Multi Board Computer [message #9144 is a reply to message #9143]

Tue, 21 September 2021 06:58

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
Please review these updated Z80 MBC boards and let me know if you have any changes/corrections/updates. Changing to smaller LEDs to recover some PCB real estate.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9147 is a reply to message #9098]

Tue, 21 September 2021 12:20

cmacarthur
Messages: 26
Registered: April 2018
Location: Alberta / Montana

Junior Member

FYI
I did a PROPIO for the RC2014 on a 75x100 board
https://easyeda.com/cmacarthur/rc2014-propio-v2-3

so you should be able to get it on 100x100
THX
CM

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Re: Z80 Multi Board Computer [message #9148 is a reply to message #9147]

Tue, 21 September 2021 13:57

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
Yes, that's the plan but not for a while. Have a backlog of PCBs to work through first although it is on the list. Have to make sure these core boards are working robustly so there are no problems on initial build. It takes a while sometimes to shake out all those subtle usability bugs but we're getting there.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9153 is a reply to message #9095]

Thu, 23 September 2021 14:37

cmacarthur
Messages: 26
Registered: April 2018
Location: Alberta / Montana

Junior Member

RE Z80 keyboard and mouse board
GREAT BORAD but I think you could eliminate the 74LS04

I believe by connecting bM1# to pin 2 (P0) of the 74LS688 and bIORQ# directly to pin 1 (G) of the 74LS688 the 74LS04 would no longer be needed.

CM

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Re: Z80 Multi Board Computer [message #9163 is a reply to message #9153]

Sun, 26 September 2021 13:14

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi CM
Excellent idea! I will do that. Seems kind of a waste for a whole 74ls04 for just one inverter. Thank you! Much appreciated, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9164 is a reply to message #9130]

Sun, 26 September 2021 13:41

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

lynchaj wrote on Thu, 16 September 2021 19:34

Hi
Z80 DMA is built and started testing. Here is an early copy of the DMA monitor program called DMAmon used to verify DMA operation.

This is an early copy and does not fully work yet. Still in development

Thanks, Andrew Lynch

Z80 DMA board is now working with minor correction. Phil making update to DMAmon program to add some features and a menu. Seems to be working with board so major progress recently. Yay!

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Re: Z80 Multi Board Computer [message #9165 is a reply to message #9164]

Sun, 26 September 2021 16:05

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi,
Current status of Z80 MBC. Making big progress lately.

/forum/index.php?t=getfile&id=2421&private=0

/forum/index.php?t=getfile&id=2422&private=0

pictured are both Red and Green Z80 MBCs. Red has prototype DSKY next gen (missing PPI extension cable). Green has Advanced DSKY. Missing 1.44MB floppy drive however both Red and Green have Z80 FDC boards so its just a matter of connecting the drive. Not enough room on the workbench. Red and Green both have Z80 DMA boards installed and working. Green's is completed except for DMA xfer LED controller. Red's Z80 DMA is almost complete except for missing SIP-9 resistor pack and DMA xfer LED controller. Also shown is RomWBW running on Green.

Boards installed on both Red and Green:
Z80 backplane V1 (uses 9V DC unregulated wall adapter power supply & LM7805 VR or Pololu 5V DC VR)
Z80 processor V2 (non-working IM2 circuit, requires work-around fix to use, addressed in V3)
Z80 clock V2 (Green is 5/10 MHz, Red is 8 MHz)
Z80 ROM V1 (1024KB, 29F040 Flash)
Z80 RAM V2 (1024KB, AS6C4008 SRAM)
Z80 serial V2 (SC16C650BIN40 w/FIFO & AFC)
Z80 PPIDE V1 (CF adapters)
Z80 FDC V1 (usually 1.44 MB Floppy drive, not pictured)
Z80 DMA V1 (almost complete except missing a couple parts, still works though)

Gerbers for all of these boards available in this thread if you want to build your own Z80 MBC. Now is a good time since a lot of the early bugs have been strained out through some PCB respins. More work continues though and additional boards coming soon.

Thanks, Andrew Lynch

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[Updated on: Mon, 27 September 2021 05:01]

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Re: Z80 Multi Board Computer [message #9178 is a reply to message #9164]

Sun, 03 October 2021 09:29

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi,
Quite a bit of news for Z80 MBC this week. The Z80 DMA board is working and has been integrated into RomWBW. Thanks to Phillip the Z80 DMA can do memory-to-memory transfers as part of the Flash File System. Using 39SF040 Flash ROMs the Z80 DMA handles the transfers to and from memory. At this point I think the project is a success and all that's left is further development of more integrated drivers into RomWBW especially for IO devices. Really good news though that it works.

Also the PCBs for the Z80 processor V3 with updated IM2 circuit and Z80 RAM V3 with revised non-volatile memory controller have arrived. I've started building Z80 processor V3 and about half way complete. Looking forward to getting that project rolling too.

Once the Z80 processor V3 and Z80 RAM V3 are built and tested and assuming no major problems the next boards will be a Z80 serial V3 with PLCC-44 UART for greater selection of AFC capable ICs. Also the Z80 DUART which will support the TI TL16C2552FN. The Z80 DUART is not a replacement for the Z80 serial board because it occupies 16 contiguous IO ports and the Z80 serial uses only 8 however for legacy compatibility reasons it must be at $68 which won't work for the Z80 DUART. So it is more of a complimentary board to bring the basic system up from one serial port to three. I think this should handle almost all of the need for extra serial ports.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9179 is a reply to message #9178]

Mon, 04 October 2021 04:15

b1ackmai1er
Messages: 396
Registered: November 2017

Senior Member

Hi Andrew,

Because this is a new system and still in development, you don't have to limit the MBC to "backward compatability" with 16650 DIP-40 based serial port as the "std" install.

If you want to defined a DUART as the base install, I think that would be pretty cool. Define your port map however you want.

Best Wishes Phil.

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Re: Z80 Multi Board Computer [message #9180 is a reply to message #8396]

Wed, 06 October 2021 04:10

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 Serial V3

/forum/index.php?t=getfile&id=2432&private=0

The purpose of the Z80 Serial V3 board is to provide greater UART part availability for AFC enabled UARTs. Functionally it is identical to the Z80 Serial V2 board with the exception of the UART using a PLCC-44 instead of DIP-40 footprint. Everything else is the same and no bug fixes. This board provides legacy compatibility with previous Z80 MBC serial boards and also the Z80 SBC designs. This is intended to be the primary console for most Z80 MBCs

Ordered PCBs so they should arrive late this week or possibly early next week. Posted Gerber files so if you'd like your own you can order from JLCPCB or any other board manufacturer you like.

Thanks, Andrew Lynch

Update: PCBs arrived, look good

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[Updated on: Tue, 19 October 2021 05:00]

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Re: Z80 Multi Board Computer [message #9181 is a reply to message #8396]

Wed, 06 October 2021 04:15

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 DUART

/forum/index.php?t=getfile&id=2436&private=0

The purpose of the Z80 DUART board is to provide multiple independent serial ports. It uses the PLCC-44 footprint dual ACE TL16C2552FN UART for two serial ports. Each port has TTL serial and real RS-232 connections. The first real serial port has top of board connector and the second is embedded in the body of the PCB. It is not backwards compatible with the Z80 Serial boards because it requires a full 16 byte IO port addresses and cannot start at the legacy $68 compatible with previous Z80 MBC serial and SBC boards. It is meant to be used in addition to Z80 serial board to provide a total of three independent serial ports.

Ordered PCBs for Z80 DUART board. Should arrive later this week or early next week. Looking forward to build and test of Z80 DUART to see how it integrates with rest of Z80 MBC system. Gerber files are posted so you can order your own board from JLCPCB or any other PCB manufacturer you choose.

Thanks, Andrew Lynch

Update: PCBs arrived from JLCPCB and look good. Distributing my excess boards to the US-based team. If anyone else would like to join up and build your own Z80 MBC system just go ahead and order your PCBs from JLCPCB

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[Updated on: Tue, 19 October 2021 05:00]

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Re: Z80 Multi Board Computer [message #9243 is a reply to message #9181]

Tue, 19 October 2021 05:01

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 ROM V2

/forum/index.php?t=getfile&id=2458&private=0

Hi
updated data files for Z80 ROM V2 respin of original Z80 ROM board. There were no problems corrected only bringing the board in line with rest of boards improvements like 3mm LEDs, mounting holes, component labeling, etc.

If you see any issues or would like to discuss changes please let me know. I plan to send these to manufacturing in a couple of weeks so there is time for revisions as needed.

Thanks, Andrew Lynch

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[Updated on: Sun, 24 October 2021 08:41]

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Re: Z80 Multi Board Computer [message #9244 is a reply to message #9243]

Tue, 19 October 2021 05:02

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 PPIDE V2

/forum/index.php?t=getfile&id=2462&private=0

Hi

This is another board respin not to fix problems but to incorporate the latest changes from other boards so the Z80 PPIDE is more consistent with the rest. Again, this board is probably not headed to manufacturing for another couple of weeks so there is plenty of time if anyone sees problems or would like to discuss changes to the board design. I am always glad to hear from you and your ideas.

Thanks, Andrew Lynch

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[Updated on: Sun, 24 October 2021 08:52]

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Re: Z80 Multi Board Computer [message #9245 is a reply to message #9244]

Tue, 19 October 2021 05:17

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 backplane V2

/forum/index.php?t=getfile&id=2452&private=0

Hi
So I had some spare time this weekend and decided to start working on the respin of the Z80 backplane board. I've been putting this one off as long as possible because I know it is a can of worms and has a lot of issues. The original Z80 backplane board has actually held up pretty well but it is out of room with the boards we have now. Also expanding it raises a lot of complexity.

First, I eliminated the LM7805 voltage regulator circuit. It works fine for 8 small boards but that's about it. I replaced it with a pair of screw terminals for 5V and GND directly from a regulated power supply like a Meanwell unit or a recycled PC power supply.

I added more slots going from 8 to 16 total slots. Also finally defined the 10 spares signals: they are VCC, GND, TEND, DREQ, I2C_RX, I2C_TX, IEI, IEO, BAI, and BAO. The last four are Zilog interrupt priority chaining and I think I came up with a solid approach using pin headers and shunts to chain together interrupt signals.

Increased the power trace width for VCC and GND from 1mm to 2mm which should handle the increased current capacity. Added 22 uF of bulk capacitance per slot inline with the backplane. That should help with the power sag issues some people saw. Put in a power switch on the board since some people saw issues with inline power switches. I dread adding switches because they are not handled well in KiCAD. There are few proper switch footprints and a multitude of choices to pick from at the vendors. This makes selection very challenging to get a match.

Finally added a special connector for 8 of the slots to carry the Z80180 extra signals: they are A16, A17, A18, A19, INT1, INT2, TEND1, DREQ1, PHI, E, ST, VCC, GND, SPARE0, SPARE1, and SPARE2. I had thoughts about expanding the data bus to 16 bits and the address bus to 24 bits but there really wasn't enough pins in the extra connector to handle them all without dramatically widening the PCB. My thinking is only about half the slots would need the expansion connector because most boards would still just use the Z80 signals only and not need the others.

The changes open the possibility for Z80180 style CPU and memory boards but kind of close off the possibilities for wider bus processors. At this point that's probably OK because this design is very 8 bit and Zilog specific. It would be hard to adapt it to other processors like 80286 or 68000 without a major redesign.

Thoughts, comments, questions? Thanks, Andrew Lynch

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[Updated on: Fri, 22 October 2021 15:59]

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Re: Z80 Multi Board Computer [message #9263 is a reply to message #9181]

Wed, 20 October 2021 17:39

coredump
Messages: 33
Registered: January 2020
Location: Germany

Member

lynchaj wrote on Wed, 06 October 2021 13:15

It is not backwards compatible with the Z80 Serial boards because it requires a full 16 byte IO port addresses and cannot start at the legacy $68 compatible with previous Z80 MBC serial and SBC boards.

Maybe it's well worth the effort to make it compatible?
Please find attached a simple draft (pullups, jumpers etc. missing), showing up one way how this might be done.
The circuit allows to set the addresses for both channels independently, eg.UART A @ $68, UART B @ $80.
At the cost of a 2nd '688 and an and gate.

Best regards
Detlef

Attachment: address_comparator_draft.pdf
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Re: Z80 Multi Board Computer [message #9268 is a reply to message #9263]

Thu, 21 October 2021 04:36

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi Detlef
You have an excellent idea. I've already made the PCBs for the Z80 DUART board and going to build a couple and see how they work out. However, I am considering some changes to the design such as what you suggest above and also converting to a quad-UART. Due to increased PCB space requirements this means elimination of the real RS-232 level connectors (MAX232 and related circuitry) and using just the TTL serial to USB connectors instead. Nothing firm yet but considering these ideas. I've been using the single serial port as console for a long while and it seems to work fine. However if someone needs multiple serial ports it is likely they'll need more than two. It really depends on what you want to do with your system.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9269 is a reply to message #9268]

Thu, 21 October 2021 04:39

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi

Just a note, I added a list of all the current Z80 MBC boards to the top-most message in this thread. I tried to add links to the data files as well but the URLs kept getting mangled by the editor even when quoted. So I attached a text file with the list of Z80 boards and links to find the latest configurations. My plan is to migrate the status of boards page over to the wiki since this thread has gotten quite large and it can be difficult for people to find things in it. Also there has been several board respins lately which is further complicating matters.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9277 is a reply to message #9269]

Sat, 23 October 2021 06:27

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
So regarding the Z80 backplane V2 redesign (4 messages back), the special connector for Z80180 signals has 16 positions and only 13 are presently used and three are designated spares. My question is whether there are other signals that would make sense to add instead of leaving the three spare signals. Z80180 supports three total interrupts which are present on the bus plus the Zilog prioritized scheme and the IM2 circuitry. I've looked over the ECB definitions and not seeing anything leap out at me as essential. If anyone has ideas on what to do with those remaining three signals please let me know.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9285 is a reply to message #9277]

Sun, 24 October 2021 09:01

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
I updated the Z80 ROM V2 and Z80 PPIDE V2 posts above with technical data for people to review when they get a chance. These two boards haven't really had any problems as far as I can tell but needed to be updated to conform with the rest of the other boards improvements like 3mm LEDs, mounting holes, component labeling, and other improvements. Also Z80 PPIDE had to move the PPI connector to on board itself and off the top portion because there isn't enough room for everything. However the new arrangement allows for the PPI connector to be preserved for legacy components assuming a flat backed ribbon cable connector.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9303 is a reply to message #9277]

Wed, 27 October 2021 10:42

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
Updated schematic and 3D render of Z80 backplane V2. Please take a look and send me your comments/questions. The secondary connectors are for Z80180 support extended signals. There are screw terminals on the back side of the PCB for the power connections (5VDC and GND only)

/forum/index.php?t=getfile&id=2485&private=0

/forum/index.php?t=getfile&id=2485&private=0

Thanks, Andrew Lynch

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Attachment: Z80BCKPLN2-schematic.pdf
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[Updated on: Mon, 08 November 2021 09:00]

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Re: Z80 Multi Board Computer [message #9341 is a reply to message #9303]

Wed, 03 November 2021 04:27

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
I went ahead and ordered some Z80 backplane V2 boards. It is a lot earlier than I was planning but in recent days working with the Z80 MBC the number of boards available fills the Z80 backplane V1 so in order to test new boards I have to remove older ones. However, removing older boards like Z80 FDC effect the configuration of the system and moves things around. Not a show stopper but an annoyance so my plan is to get the new larger backplane and use the older backplane for testing.

Another change is the current capacity of a full backplane is really stretching the limits of the LM7805 voltage regulator. It still works but you can tell it is straining under the load and generating a lot of heat. 8 slots is pretty much the maximum it is going to support I believe. The larger backplane will use screw terminals for 5 VDC directly from an external power supply which should spread the heat burden out more and push some of it back into the power supply. In my case I am going to use an older mini pre-ATX type power supply with an internal fan for 5V DC and GND. It will also power the floppy drive for some bench top space savings as well.

Over time my view of Z80 MBC has kind of evolved somewhat. Previously I was very reluctant to do PCB respins unless there was an absolute show stopper defect which there have been a couple (Z80 processor V2 and Z80 RAM V1). Now I see respins somewhat more liberally because they really make things easier by fixing relatively minor bugs and allow improved techniques to be rolled into older boards. Even those without outright defects can benefit from respins quite a bit so they are a good thing. JLCPCB has lowered the cost of respins so much compared to the Z80 SBC days when any change to a PCB other than the silkscreen induced a tooling fee charge of $20 or more to even consider changing a design in addition to board manufacturing and shipping costs. The price of JLCPCB boards is much lower and more frequent PCB respins are a lot more affordable now. Also the modular design of the Z80 MBC sort of lends it self to PCB respins because problems with subsystems can be isolated to a single board and doesn't require a respin of the entire system to make even a small fix.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9379 is a reply to message #9341]

Sun, 14 November 2021 18:12

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi

I built the Z80 backplane V2 today and it works fine. It uses direct 5V DC from a regulated power supply like an old ATX or bench top power supply. Having 16 slots makes testing new boards much easier because you don't have to take out the old ones to install new ones.

The Z80 DUART seems to work fine but there are some issues with the receive and transmit LEDs so there will be a Z80 DUART V2 eventually to fix the problems.

Also found out that I was experiencing some instability (aka "bad ints") on one of my systems (Green) and it turned out to be the "clock 50%" jumper on the Z80 clock V2 board. I replaced the 10 MHz oscillator with an 8 MHz one and removed the "clock 50%" jumper and that seems to have resolved the occasional instability. The Red system had an 8MHz clock without the "clock 50%" jumper and has been rock solid.
The system can go faster but there is an 8 MHz DMA chip on board and I do not want to overclock while testing software. Interesting discovery.

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9393 is a reply to message #9379]

Thu, 18 November 2021 06:24

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
I updated the Z80 DMA and Z80 clock V2 board entries in this thread with recent discoveries. In short the Z80 DMA board driver has been updated and now if it is not connected to external IO device like the Z80 FDC it needs to have pins 2-3 jumpered on the "EXT DMA" connector to work properly. Also the Z80 clock V2 board in some instances can cause instability if the "clk sel" jumper is installed and the 50%/100% clock mode enabled. Using the full time 100% clock mode runs more stably on one of my systems and prevents spurious "bad int" messages in RomWBW

Thanks, Andrew Lynch

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Re: Z80 Multi Board Computer [message #9435 is a reply to message #9393]

Mon, 29 November 2021 12:22

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 ROM V2 board

/forum/index.php?t=getfile&id=2505&private=0

Update: PCB has gone to production and expect delivery sometime next week

update: PCBs arrived with no problems. Build and tested and works fine. Very nice!

Attachment: Z80ROM2.html
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Attachment: Z80ROM2-schematic.pdf
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[Updated on: Thu, 23 December 2021 08:43]

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Re: Z80 Multi Board Computer [message #9436 is a reply to message #9435]

Mon, 29 November 2021 12:24

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Z80 PPIDE V2 board

/forum/index.php?t=getfile&id=2513&private=0

Update: PCB has gone to production and expect delivery sometime next week

update: PCBs arrived with no problems. Built and tested and work great. Super!

Attachment: Z80PPIDE2-Gerbers.zip
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Attachment: Z80PPIDE2-schematic.pdf
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[Updated on: Thu, 23 December 2021 08:44]

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