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Home » RBC Forums » General Discussion » New board: RC-Z8BASIC (Zilog Z8671 aka Z0867108) (A Z8 BASIC/DEBUG (Z8671 aka Z0867108) SBC with 128KB SRAM and battery backup, RS-232, USB adapter port, GPIO port, LCD (1602 or 2004) port, User led and key, ROM emulation mode, on-board PS)
New board: RC-Z8BASIC (Zilog Z8671 aka Z0867108) [message #6424] Sun, 28 July 2019 10:09 Go to next message
just4fun is currently offline  just4fun
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Some weeks ago I've found a "forgotten" Z8 BASIC (Z8671 aka Z0867108) MCU.
Using a simple test the MCU seemed to work:

/forum/index.php?t=getfile&id=1447&private=0
/forum/index.php?t=getfile&id=1448&private=0

So I've decided to give it a new "home" (= a board...) and after some readings I've done a first draft design.

The specs are:

128KB SRAM with battery backup, RS-232 port, serial-USB adapter port, GPIO port, User led and key, on-board power supply, ROM emulation mode to enable the "Auto execution on power-up" feature, can be powered from USB or on-board power supply.

Next step will be import the handmade schematic into Kicad and make the PCB...




[Updated on: Tue, 15 October 2019 03:26]

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Re: Starting a new board: RC-Z8BASIC [message #6425 is a reply to message #6424] Wed, 31 July 2019 03:02 Go to previous messageGo to next message
b1ackmai1er is currently offline  b1ackmai1er
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Interesting Smile

Datasheet https://kundoc.com/download/z8-single-chip-family-extended_5 a7e8aced64ab254ee8ea4bf.html

https://cdn.hackaday.io/files/260591114908256/Z8671%20App%20 Note.pdf

[Updated on: Wed, 31 July 2019 03:04]

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Re: Starting a new board: RC-Z8BASIC [message #6426 is a reply to message #6425] Wed, 31 July 2019 05:17 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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@b1ackmai1er: thanks for the links...

Here the draft of the schematic:

/forum/index.php?t=getfile&id=1459&private=0

EDIT: Updated schematic

[Updated on: Thu, 08 August 2019 04:29]

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Re: Starting a new board: RC-Z8BASIC [message #6431 is a reply to message #6426] Mon, 05 August 2019 00:36 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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This is how the PCB will be...

/forum/index.php?t=getfile&id=1460&private=0

/forum/index.php?t=getfile&id=1461&private=0

EDIT: new PCB rendering

[Updated on: Thu, 08 August 2019 04:37]

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Re: Starting a new board: RC-Z8BASIC [message #6470 is a reply to message #6431] Thu, 22 August 2019 02:32 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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After a first checking phase I've done some changes.
Now it is possible to choice two different schemes of ROM emulation (some RAM behaves as ROM). Probably the most useful is the 32K ROM / 32K RAM.

/forum/index.php?t=getfile&id=1477&private=0

/forum/index.php?t=getfile&id=1476&private=0
Re: Starting a new board: RC-Z8BASIC [message #6486 is a reply to message #6470] Tue, 27 August 2019 01:44 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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I've found a possible problem with R10 that limits the injected current from the RC-Z8BASIC board to the serial-USB adapter when the board is powered from the on-board PS and the serial-USB adapter is not powered from the USB:

/forum/index.php?t=getfile&id=1492&private=0

During normal operations R10 can act as a "reversed" voltage divider if the serial-USB adapter has internally a led directly connected to the RX line. An example is the common (bad designed) CH340 serial-USB adapter module that has a RX led with R3 as limiting resistor:

/forum/index.php?t=getfile&id=1493&private=0

The result is that the RX signal remains always at the "1" level.

I've done some tests and the only serial-USB adapter that doesn't seem to show this problem is the FTDI based one.

Because I don't like this limitation, I want find a solution (without increasing the number of ICs)... and may be I found it, but I have to do some tests before...

[Updated on: Tue, 27 August 2019 01:59]

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Re: Starting a new board: RC-Z8BASIC [message #6512 is a reply to message #6486] Mon, 02 September 2019 04:07 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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I think that it should be ok now. No more serial-USB limitations! (and I've done a little optimization too...)

Time to send it to the service is near...

/forum/index.php?t=getfile&id=1499&private=0

/forum/index.php?t=getfile&id=1498&private=0

[Updated on: Mon, 02 September 2019 04:19]

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Re: Starting a new board: RC-Z8BASIC [message #6629 is a reply to message #6512] Mon, 07 October 2019 03:35 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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The PCB is arrived a last...

https://i.postimg.cc/BvDZ4d9Q/20191007-121839.jpg
Re: Starting a new board: RC-Z8BASIC [message #6630 is a reply to message #6629] Mon, 07 October 2019 06:51 Go to previous messageGo to next message
b1ackmai1er is currently offline  b1ackmai1er
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Looks Great!

Regards Phil.
Re: Starting a new board: RC-Z8BASIC [message #6647 is a reply to message #6630] Fri, 11 October 2019 00:14 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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Starting to seem a real thing... Cool

/forum/index.php?t=getfile&id=1540&private=0

Now I've to write a Basic program to play with the LCD...
Re: Starting a new board: RC-Z8BASIC [message #6651 is a reply to message #6647] Sat, 12 October 2019 12:15 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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LCD now works too... Smile

https://i.postimg.cc/Gt4g29XT/20191012-202646.jpg
Re: Starting a new board: RC-Z8BASIC [message #6666 is a reply to message #6651] Tue, 15 October 2019 03:25 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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All the details and info to build a RC-Z8BASIC board are here! Cool

(Attached here the final version of the schematic)

[Updated on: Tue, 15 October 2019 05:02]

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Re: Starting a new board: RC-Z8BASIC [message #6708 is a reply to message #6666] Fri, 25 October 2019 11:28 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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Some days ago I found a seller on ebay (from Poland) who was selling UB8830D chips, the clone of the Zilog Z8671 made in the "East Europe".
The price was good so I decided to try to buy a couple of them:

https://i.postimg.cc/SsYHrttK/20191025-111356-B.jpg

Unfortunately they seem not to be working at all.

I've also done the same simple test on the breadboard that I did at first with the Zilog Z8671:

https://i.postimg.cc/pXCcDHXZ/20191025-122914.jpg

It shows a 60mA more higher current (170mA vs 110mA) and higher heat, but without any working output on the serial port... Crying or Very Sad

The seller says on his insertion that it is equivalent with Zilog Z8611 (4K bytes generic ROM version), while accordingly with some google searches and with the attached pdf the UB8830D is equivalent to the Zilog Z8671.

May be a "East Europe" relabeled chip... Rolling Eyes


[Updated on: Fri, 25 October 2019 11:29]

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Re: Starting a new board: RC-Z8BASIC [message #6710 is a reply to message #6708] Fri, 25 October 2019 15:49 Go to previous messageGo to next message
gkaufman is currently offline  gkaufman
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That's not good news, I have 10 on order Sad
Re: Starting a new board: RC-Z8BASIC [message #6711 is a reply to message #6710] Sat, 26 October 2019 00:57 Go to previous messageGo to next message
b1ackmai1er is currently offline  b1ackmai1er
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Opened the attachement and learnt some german words which seem quite appropriate ...


ist nicht nutzbar



Re: Starting a new board: RC-Z8BASIC [message #6713 is a reply to message #6711] Sat, 26 October 2019 01:54 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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About "ist nicht nutzbar" I've found an interesting paper about the U8611 (=Z8611)... see the attachment

der U8611 ist ein Einchipmikrorechner, bei dem der interne 4k ROM nicht nutzbar ist:
durch Pegel von 7,35v bis 8V on reset Sprung auf externen Programmspeicher 1012H;
Port 0 und 1 werden für die Adressen- und Datenverkehr genutzt;

So it seems that if it is applied a voltage between 7.35V and 8V on the reset pin, a jump to the 0x1012 external memory location is done...

There is no mention on that on the original Z8611 datasheet...

[Updated on: Sat, 26 October 2019 02:03]

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Re: Starting a new board: RC-Z8BASIC [message #6714 is a reply to message #6713] Sat, 26 October 2019 04:10 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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I've found a Zilog application notes about the Z8 Test Mode that is enabled pulling the RESET pin at Vcc + 2.5V.

See the attachment...

Note that in the "Program B listing" example the program on the external memory starts at 0x0812 as stated on the U8611 sheet for a 2K bytes ROM Z8 chip.

BTW: this can be a way to check if a Z8 ROM-med MCU has a 2K or 4K ROM.. if it jumps to 0x0812 is a 2K ROM model, if jumps to 0x1012 is a 4K ROM one...

Of course you need a LA on A8-A15 (to see a 08H or a 10H) using the AS signal L->H transition as trigger (see the ext mem R/W timing on the datasheet).


[Updated on: Sat, 26 October 2019 10:52]

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Re: Starting a new board: RC-Z8BASIC [message #6721 is a reply to message #6714] Tue, 29 October 2019 13:02 Go to previous messageGo to next message
gkaufman is currently offline  gkaufman
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Another German page with useful information about the U8830D: https://hc-ddr.hucki.net › doku.php › elektronik:u883

Unfortunately I don't speak German, but using Google Translate:

From Zilog there is the Z8671, a Z8601 with integrated TINY-BASIC. This variant corresponds
not at all the U883 !! Neither the BASIC description nor the PROM hex dump
correspond to those of the U883. Thus, the Z8671 is not a substitute for the U883

The single chip microcomputer U883 contains a simple 2K byte internal ROM
BASIC interpreter. In addition, there is a corresponding editor / debugger part, which contains all functions, the
are necessary for program development. These components are either in the
external ROM, they can be omitted after completion of development work, or they exist
a host computer.

Re: Starting a new board: RC-Z8BASIC [message #6723 is a reply to message #6721] Wed, 30 October 2019 01:42 Go to previous messageGo to next message
just4fun is currently offline  just4fun
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Wow... this really change things!

As far I can see this ROM Basic needs an external (assembler) starting routine to make it work.

In the example (see 8.5) it seems that there are three jump vectors:

812H is the "starting" assembler routine;
815H is the jump to the input routine (GET_CHAR);
818H is the jump to the output routine (PUT_CHAR);


So to try to use this MCU with the RC-Z8BASIC it is needed to find a way to put the needed code inside the SRAM...

(but to use easily this MCU with the RC-Z8BASIC changes must be done as a simple SRAM is not enough... probably a "companion" MCU to help to load a generic binary into the SRAM as it seems that the "user case" is radically different and similar to a romless Z8 assumed that an external host is always required...)


BTW: In the example are used three programs to compile (the first should be the assembler, the others utilities):

%bin%\as.exe -L %file%.asm -a
%bin%\p2bin.exe -r $-$ "%file%.p"
%bin%\plist.exe "%file%.p"

[Updated on: Wed, 30 October 2019 11:29]

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Re: New board: RC-Z8BASIC (Zilog Z8671 aka Z0867108) [message #6734 is a reply to message #6424] Wed, 06 November 2019 01:24 Go to previous messageGo to next message
b1ackmai1er is currently offline  b1ackmai1er
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Boards arrived ... can't beleive I didnt order them in blue Sad

Now for the aliexpress dance - damn I don't have a 74LS69057663, wait 2 months, now I have 9 spares ;)

Thanks.
Re: New board: RC-Z8BASIC (Zilog Z8671 aka Z0867108) [message #6736 is a reply to message #6734] Wed, 06 November 2019 07:42 Go to previous messageGo to next message
gkaufman is currently offline  gkaufman
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There's always Digikey Smile Lately I've been getting my orders in 48 hours with Priority mail.

On Aliexpress watch the shipping choice. China Post is pretty reasonable, as is Ali Standard Shipping. Both seem to take about 2 weeks from when it is actually shipped (not when a tracking # is generated). Yanwen, SunYou or Cainino must be using a Kayak to get it here from China as it often runs 60+ days to arrive. The difference in cost is often just a few cents.

- Gary

b1ackmai1er wrote on Wed, 06 November 2019 01:24
Boards arrived ... can't beleive I didnt order them in blue Sad

Now for the aliexpress dance - damn I don't have a 74LS69057663, wait 2 months, now I have 9 spares ;)

Thanks.
Re: New board: RC-Z8BASIC (Zilog Z8671 aka Z0867108) [message #6737 is a reply to message #6736] Wed, 06 November 2019 14:14 Go to previous messageGo to next message
b1ackmai1er is currently offline  b1ackmai1er
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Good advice, thanks. Yes I noticed Yanwen are very slow in particular. I guess this stuff must be travelling by sea freight like you said.

Actually I'm pretty grateful to aliexpress and I could be more organized with my parts list ordering. I use UTsource a lot more now but sometime it takes time to gather up a parcel of parts to meet the free postage requirement otherwise the shipping cost is prohibitive.

Regards Phil.
Re: New board: RC-Z8BASIC (Zilog Z8671 aka Z0867108) [message #6761 is a reply to message #6737] Wed, 13 November 2019 07:10 Go to previous messageGo to next message
gkaufman is currently offline  gkaufman
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Board went together nicely, and powered up the first time. Thanks for a fun project, and excellent instructions (especially on setting the baud rate and adjusting the vector for autorunning a basic program).

Wish the U8830D had worked out, as Z8671's are fairly uncommon.

If you were to redesign with an extra Eprom socket it might be possible to both accommodate the U8830D or use a rom-less Z8 with tiny basic in external eprom Smile

- Gary

Re: New board: RC-Z8BASIC (Zilog Z8671 aka Z0867108) [message #6769 is a reply to message #6761] Thu, 14 November 2019 01:02 Go to previous message
just4fun is currently offline  just4fun
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Thanks!

About the U8830, somethings else must be added, may be an EPROM/FLASH or an other MCU to help at the boot time (I mean like the Z80-MBC2 approach) if the Z8 bus can be easily three-stated.
Doing that will make the use of a rom-less Z8 feasible for sure.
The "problem" is that currently I've a full "to do" list (for my little spare time), so I don't know if/when I could do it....

BTW: currently I'm making a board with a STM32F030R8 (ARM Cortex M0) with an "unusual" PCB to act as a "normal" dev board or as a breakout board for 1/4 breadboards:

/forum/index.php?t=getfile&id=1568&private=0

https://i.postimg.cc/j2r9hNyC/20191103-102158.jpg

Having a lot of 5V tolerant GPIO, I'd like to use it to play with a 68008 CPU... But this one is an other "story"... Cool
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