In this section you can find a few add-on cards made by me, some researches I made to discover more about this computer, and some related projects.

All cards in this section were built and they are working.

Add-ons made:

• 56 KBytes static RAM expansion
• Multi-firmware Eprom card
• PS/2 keyboard interface
• Eprom patch for video-graphic card

Researches:

• Hard-disk
• Floppy-disk format
• Eprom patch for video-graphic board
• Expanding ram up to 60K
• S.O.N.E. listings
• Hand-made eprom listings
• Modified 382 eprom

Other projects:

• Rebuild of a simplified version of the computer (by Pietro De Luca): A Z80 VERSION 2006 (italian only)
• Computer replica (by Paolo Pinto): Z80 NE REPLICA
• Piergiorgio Betti repository, containing a lof of software and documentation (mainly for CP/M): https://github.com/pbetti/ZDS
  A Piergiorgio Betti repository mirror updated at 01/01/2024 is available here
• EPROM emulator (by Andrea Barbadoro and Paolo Carrer): EPROM EMULATOR (italian only)
• Andrea Barbadoro Google Drive disk, containing various projects in developing state: https://drive.google.com
  A mirror of the Google Drive disk updated at 21/10/2024 is available here

56 KBYTES STATIC RAM EXPANSION

56 Kbytes static RAM expansion

This card is a 56 KBytes memory expansion.

I chose to realize a 56K card instead of 64K because the addresses starting from EC00h are occupied by video memory of the card LX.388, and then by firmware of the floppy disk interface LX.390 (starting from F000h).

So the card is mapped from 0000h to DFFFh including. For this reason is not possibile to use the hexadecimal monitor eprom that is on the CPU card LX.382 that is mapped from 8000h to 83FFh, and the two 2114 ram chips that are on the same CPU card that are mapped from 0000h to 03FFh, and also the eprom programmer firmware LX.394-395 that is mapped from 8400h to 87FFh.

To use these firmwares together with this card it's necessary to build the card with multi-firmware eprom also, as explained below in this section.

To disable the hexadecimal monitor firmware and two 2114 ram on the CPU card LX.382 it's necessary to operate as explained in the article COME ESPANDERE LA MEMORIA NEL COMPUTER published on magazine number 77.

This expansion card is relatively simple, because it uses only one 128 KBytes static memory chip TC551001 made by Toshiba, that has a very low power usage, of which it's used only the first 56 KBytes. Due to the fact it's a static memory chip, it doesn't need refresh for dynamic memories like that one implemented on the 32K dynamic ram expansion LX.392, making schematic alot easier.

Address decoding is done by U4 chip, a 74LS85 used as binary comparator that, together with logic implemented by U7 and U8, respectively a 74LS00 and a 74LS32, enables the ram for all addresses between 0000h and DFFFh for memory read and write operations.

U1 and U2 buffers could also be omitted. In my computer I used them to make signals a bit more stable due to the high number of cards.

Warning: this card can work properly only if the ENH signal is present on the bus. Due to the fact that this signal is generated by LX.390 floppy-disk interface or by card with multi-firmware eprom, at least one of these cards must be present on the bus.

56 KBytes static ram expansion schematic (423 KB)

56 KBytes static ram expansion pcb layout (53 KB)

(contains the complete project file in EDWIN format and pcb images)

Paolo Pinto made a new pcb layout in GERBER format, very professional, starting from the schematics.

It's available in the printed circuit boards section.

Components list:

Note: all capacitors are near chips power pins.

MULTI-FIRMWARE EPROM CARD (Version 1.4)

Multi-firmware eprom card

This card permits to use a personalized firmware that makes it possible to boot all operative systems and all hexadecimal monitors that were made for this computer, plus a program to convert floppy disks datamarks and a program to test ram.

Using this firmware, at the machine startup a menù will be shown through which it's possible to launch all monitors, boots and available programs.

To use this card it's necessary to disable all eproms that are present in the computer, both the eprom on the CPU card LX.382 and that one on the floppy disk interface LX.390, as explained below.

This card can work with a 27C010 eprom or a 27C020 eprom, respectively by 128 or 256 KBytes. Instead of eproms it's possible to use more modern flash memory 29EE010 or 39SF010A, 39SF020A, 39SF040A (NOTE: to use 39SF040A you must disconnect pin 1 by rising the pin or cutting its printed circuit track, so that +5V DOESN'T reach pin 1 of the flash memory).
The eproms are interchangeables without doing any change to the card (with 39SF040A flash memory exception).

The eprom is used with a memory bank tecnique. In particular there is a bank always resident and not modifiable that is mapped from F800h to FFFFh. In this bank there is the multi-boot firmware.

Then there is a bank mapped from F000h to F7FFh that is switchable by sending a byte to the I/O port 5Fh, to which this card answers.

The value sent to this I/O port selects one of possible 1 KByte banks that are in the eprom. Infact, even if the switchable bank is mapped from F000h to F7FFh so it's a 2 KBytes bank, it's possibile to address the eprom at 1 KByte blocks (because the majority of firmwares made for the computer occupy 1 KByte only).

So, the value set to I/O port 5Fh set the 1 Kbyte eprom block to be mapped starting from F000h, but if the sent value is an even number it's possible to access the next 1 KByte eprom block that will be mapped from F400h to F7FFh.

Instead if the value sent is odd there will be two times the same 1 KByte block mapped from F000h to F3FFh, and from F400h to F7FF.

So, to summarize, the eprom banks are mapped as shown in the following table:

Obviously 2 KBytes firmwares need to be put inside the eprom at an address accessible by an even bank number, while 1 KByte firmwares can be put in any bank.

As told before, at addresses mapped from F800h to FFFFh there is always the eprom content at addresses from 0800h to 0FFFh (relative to the eprom addresses starting from 0000h), that is the content of 2 Kbytes eprom bank number 2 (if the second bank will be selected, the same bank 2 will be present from F000h to F7FFh and from F800h to FFFFh at the same time).

Infact the eprom bank 2 (composed by banks 2 and 3 for 2 Kbytes total) contains the multi-boot firmware that needs to be executed at computer power-on and needs to be always available at F800h, independently from the selected bank.

This card has a reset circuit also, made by U1 chip, that at power-on always enables the eprom (and at the same time it disables all ram expansions by way of ENH bus line) for the duration of the first instruction read by the CPU. This instruction must be a JUMP to a location inside the multi-boot firmware (in the address range from F800h to FFFFh). Doing so at power-on, even if the CPU put the address 0000h on the bus to read the corresponding location, the CPU reads the instruction present at F800h (that is inside the eprom) allowing the machine start-up.

As told before, to use this card it's necessary to disable the eprom on the floppy interface LX.390.

To disable this eprom it's necessary to make the following changes to the floppy interface LX.390:

• remove IC2 chip (it's the 74LS30 at low left on the board)
• connect pin 1 of IC3 to pin2 of IC3 (the same chip - it's the 74LS08 at high left on the board)
• remove eprom IC6 (it could also be left in place)
• remove jumper P1

The following table contains the list of all files included into the multi-firmware eprom, with their bank number:

The firmware in the eprom, at computer start-up or reset shows a menu with the following options:

NOTA: if you press ESC key on a alphanumeric keyboard or CTRL+F on the hexadecimal keyboard while powering-on the computer (or while doing a reset), ram test program will be run. To to this operation the ram is not used, but it uses only Z80 internal registers. This is usefull to make a ram diagnostic in case of bad ram.

Multi-firmware eprom card schematic (486 KB)

Multi-firmware eprom card pcb layout (1.10 MB)

(contains the complete project file in EDWIN format and pcb images)

Paolo Pinto made a new pcb layout in GERBER format, very professional, starting from the schematics.

It's available in the printed circuit boards section.

Multi-firmware eprom binary full image (30 KB)

Source of firmware mapped from F800h to FFFFh (20 KB)

Assembler output (cross reference) of firmware mapped from F800h to FFFFh (53 KB)

"jump.inc" file, containing multi-firmware monitor jump table. It should be used as "include" in external programs that requires the jump table (3 KB)

NOTE: To make the binary file of the eprom starting from source, it's necessary to include also all needed firmwares. These are already included in the eprom binary full image downloadable here.

Components list:

Note: all capacitors are near chips power pins.

HARD-DISK

Luckily I got a Motorola MVME system that, as per the included documentation, uses a BASF 6188 hard-disk: incredibly there is also an add-on controller. The Motorola system has a very complete documentation, including schematics, and there is also an example circuit to connect the controller to a Z80 system. Well, I compared this circuit schematic with LX.683 interface and they are almost identical !!!!

So I discovered that the controller is a XEBEC S1410A, and that the interface is SASI standard (that is the predecessor of SCSI).

So, even if I can't be 100% sure, there are very strong possibilities that the original controller was that XEBEC, even because the two available controller photos on the magazine are 100% equals to the real XEBEC controller I got (also the printed circuit board tracks are identical).

So I built a LX.683 interface on a proto-board, I connected the hard-disk and computer, and incredibly I was able to format the hard-disk and to install SONE at the first shot.

In contrary to what stated in the Motorola system documentation, the hard-disk on this system is not a Basf 6188 but it's a Seagate ST-225. Anyway they have the same geometry and the ST-225 has only double tracks available: it shouldn't be a problem to use it instead of Basf, even if obviously it's half used.

Next I made the printed circuit board of LX.386 interface starting from the original draws, I assembled the interface and put the hard-disk and the Xebec controller into a standard SCSI-I case.

Here there are some photos:

This is the LX.683 interface built on a proto-board	Hard-disk with XEBEC S1410A controller
Hard-disk and controller rear	Hard-disk connected to LX.683 interface
XEBEC S1410A controller	Formatting started...
The hard-disk is correctly formatted at the first shot	SONE boot from hard-disk
Hard-disk directory after the system and a few files have been copied to	STAT command output that shows hard-disk size
README file available in the SONE operating system	LX.386 interface made from scratch
Seagate ST-225 hard-disk assembled into a standard SCSI-I case	Xebec S-1410A SASI controller assembled over the Seagate hard-disk

FLOPPY-DISK FORMAT

Floppy disk used with eprom 390 have the following format:

• single side / single density
• FM encoding
• 40 tracks
• 17 sectors per track, with sectors ID numbered from 1 to 17
• 128 bytes per sector
• software interleave 1:1 (sectors are in the order: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17)

NE-DOS floppy disk, used with eprom 1390 or with eprom 2390, have the following format:

• single side / single density
• FM encoding
• 40 tracks
• 10 sectors per track, with sectors ID numbered from 0 to 9
• 256 bytes per sector
• directory on track 17 (starting from 0)
• software interleave 1:5 (sectors are in the order: 0 5 1 6 2 7 3 8 4 9)

Also, thanks to researches made for the hard-disk, I was able to decode the floppy format used with eprom 683 by SONE operating system.

SONE is a CP/M 2.2 compatible system (it's almost a CP/M 2.2 clone), but the floppy format is different from any floppy I know, and it's only similar to Osborne-1 format.

The floppy format is as follows:

• single side / single density
• FM encoding
• 40 tracks
• 10 sectors per track, with sectors ID numbered from 1 to 10
• 256 bytes per sector
• directory on track 3 (starting from 0), into sectors from 1 to 8
• software interleave 1:6 (sectors are in the order: 1 7 3 9 5 2 8 4 10 6)

Formatted disks are 92 KBytes size.

SONE supports also another format (but it isn't able to format floppies) that is 17 sectors per track / 128 bytes per sector.

Then I was able to create a format parameters list to be used with Sydex 22DISK program, that lets you read/write single files on floppies using a PC.

The parameters list to be added to the existing one (by changing the CPMDISKS.DEF file as indicated in 22DISK documentation) is the following:

BEGIN Z8NE Z80 Nuova Elettronica - SSSD 48 tpi 5.25"
DENSITY FM ,LOW
CYLINDERS 80
NOTE per drive da 360K o da 720K mettere CYLINDERS 40
SIDES 1
SECTORS 10,256
SIDE1 0 1,7,3,9,5,2,8,4,10,6
BSH 4 BLM 15 EXM 1 DSM 46 DRM 63 AL0 080H AL1 0 OFS 3
END

 

PS/2 KEYBOARD INTERFACE

My friend Pino Giaquinto made a little but very usefull interface to connect a normal PS/2 keyboard to keyboard input on LX.388 and LX.529 cards.

This interface is able to manage keyboards with Italian and USA layout, and it exactly reproduces all keys and operating modes of LX.387 (and LX.387-B) keyboard with LX.549 numeric keyboard.

Building is very easy. The interface uses a PIC 16F628A micro-controller that needs to be properly programmed using the following file.

• HEX file to program PIC 16F628A
• program source for PIC 16F628A
• printed board layout
• Italian and USA keyboard layout
• PS/2 keyboard connector
• table with all scan-codes and corresponding emulated characters
• table with codes of KR2376 keyboard encoder used in the original keyboard LX.387

NEW: Here you can find the new 3.3.1 version (Italian only)

EPROM PATCH FOR VIDEO-GRAPHIC CARD

Pino Giaquinto made a patch for video-graphic board LX.529 eproms 529 and 530, to remove some little glitches.

The patch has been made to correct "_" (underscore) characted that Nuova Elettronica showed like a right arrow, also redundant because it's already present as E9h character. The same is for "^" characted that was shown as a up arrow.
So Pino moved arrows, changed the pipe "|" to be more modern, and added the inverse apex that was completely missing.

Here you can dowload patched eproms:

Eprom 529 version 2

Eprom 530 version 2

And this is the complete character map: Character map version 2

Piergiorgio Betti describes how it works:

video raster scan is generated by rows and every row is made by a series of pixels. The SY6545 controller let it define how many pixels, for height, compose a character and so a characters row (look at page 3-160 of 6545 Synertek datasheet).

In Nuova Elettronica Z80 computer this height is defined at 16 pixels so we have a character matrix of 8x16 pixels. So to define a character we need 16 bytes: every "1" bit of this matrix make a pixel on the screen to light.

Every character, that is a block of 16 bytes, is programmed into 529 and 530 eprom of LX.529 interface.
Characters are sequentially put into eprom starting from character 00h to 7Fh for 529 eprom, and from da 80h to FFh for 530 eprom.
The fact that every character is a 16 bytes block makes addressing very simple: for example into 529 eprom, characters from 00h a 7Fh have address 000h, 010h, .... 7F0h.

To verify it you can open the eprom dump image using a binary editor.

Look for capital "A" letter that has hexadecimal value of 41h and that will start at location 0410h in the eprom:

The following 16 bytes after address 0000:0410 should be the "A" letter.

In this manner is not very clear, but if we show one byte at a time we clearly can see "A" letter:

Obviously at address 0420h there will be letter "B" and so on.

So, by using this patch, the character map has changed from this:

to this:

S.O.N.E. LISTINGS

My friend Pino Giaquinto sent to me a few original listings related to S.O.N.E. They where discovered in documentation owned by of Constantinos Harikatis, that was a Nuova Elettronica developer.

They are original assembler listings of EPROM 683, listings of format programs for single and double density floppy disks (the latest never published by Nuova Elettronica), listings of S.O.N.E. Bios for single and double density, and listings of PUTSYS program that let you generate the operating system.

NOTE: eprom 683 listing is identical to the eprom content. Other listings where not verified: I have no clue if they are "officials" versions or development versions.

You can download listings in .PDF format here:

HAND-MADE EPROM LISTINGS

Biagio Paribello sent to me a few Eprom listings, hand-made and commented by himself.

They are assembler listings of EPROM 382, EPROM 390 and EPROM 394.

You can download listings in .PDF format here:

• Eprom 382
• Eprom 390
• Eprom 394

NOTE: listings related to these and also to other eproms are available in the software page.

MODIFIED 382 EPROM

Sergio Internicola found a 382 eprom, patched to be used with LX.388 video card and alphanumeric keyboard, instead of hexadecimal keyboard.
The eprom has unknown origin, it's marked "MONITOR TAST. ALF.", and it seems to work properly.
It implements the same commands of the original 382 eprom, that can be invoked by using the following keys:

M - view/edit memory
R - view/edit CPU registers
V - run program
P - run step-by-step
L - load from tape
S - save to tape
J - jump to 8400h (to be used with the eprom programmer LX.394-395)

The master-mind (the easter egg that can be run with CTRL+F in the original eprom) seems to be removed.

This eprom can be donwloaded here: ep382x.bin