ZX-Flash Cart (512 Kb in a single cart)

•   What is a ZX-Flash Cart?
•   How it works?
•   Construction of a ZX-Flash Cart
•   How to get a Interface II?
•   How to create files for the ZX-Flash Cart
•   Questions and Anwser
•   Donwloads
•   News
•   Thanks to

    The ZX-Flash Cart is a homemade Interface II compatible cart (..and compatible with its clones). It can be programed with 10 snapshots in SNA format that can be loaded in the spectrum just using a selection menu. In the download area you have available a Windows program to get ten SNAs programs and create a cart file with a selection menu included ready to program the memory of the ZXFlash cart (a 29F040).

 The original cart compared with the ZX-Flash Cart

The steeps to get a ZXFlash cart with your favorites games is dead easy. First run the program "ZXFlash Creator" (available in the download area), choose ten SNAs files and get the file to program the flash memory just clicking the "Create Flash" buttom. This file will be a 512Kb size file that you can use to program the flash memory by yourself with your own programmer (Willem or any other) or you can take this file to your favorite electroinic store in order to get a 29F040 programed with it.

In my city I can get the memory programmed for 5 Euros (3,5 Euros the memory + 1,5 Euros for the programmer service)

Once you get the memory programmed, you just need to put it on its socket, put the cart in the Interface II connector, power on and enjoy.

How it works ?

   From a "electronic" point of view this device is not complicated, but form the "software" point of view is more complicated. The Interface II conector for carts it was designed to use 16K carts, so we have not availabe there control signals as IORQ, WR etc to help us to map bigger memories in banks of 16K. So we need some "tricks" to map 512K in a 16K space.

The logic of the ZXFlash cart is was designed to detect just memory access to the address 3FFE and 3FFF, this access will generate a pulse that drive a counter. This counter controls the five upper address lines of the 29F040 in order to put availabe differents banks of 16K of memory (32 * 16 = 512). In others words, the five lines used of this counter select which 16 K bank of the 32 banks availables is selected.

To avoid change from one bank to the next while we just read its content to transfer to RAM, we don't use the first and second line of the counter. To change to the next bank we must access to the address (3FFE or 3FFF) four times instead just one. Once we have read the three banks that store a SNA, and transfered its content to RAM, the load program set the Z80 registers with the SNA header data, block the ROM mapping system to avoid future maps, and jumps to the start address of the program.

For the details see the source code available in the donwload area.

There was a problem we needed to fix, the refresh cycles of the dinamic memory generate periodically the same condition in the bus as if we were reading the memory, so this signals could create confusion in the ZXFlash Cart. Fortunely the pulse generated by the refresh cycle it was very short, so with the help of C2 1KpF the problem was eliminated. The capacity of C2 are enought to filter short pulses (refresh cycles) but so much low to eliminate real memory access.

C1 and R1 generate a reset pulse in the startup to get the bank 0 as the initial bank.

   Construction of a ZX Flash Cart.

You will need the following components:

• Positive board doble side 60 mm x 100 mm (my advice is: Covenco / Bungard model PKP-200)
• IC1: 29F040
• IC2: 74HC4040
• IC3: 74LS32
• IC4: 74S133
• D1: 1N4148
• C1: 33 uF (15v)
• C2: 1KpF
• R1 330 ohms
• 2 x 16 pins socket
• 1 x 14 pins socket
• 1 x 32 pins socket
• All the chemical you need to develop printed circuit boards. (developer, etching fluid, etc)

In the donwload area you can get all the files you need for the construction of the printed circuit board. Also you can find the files in Eagle format.

The construction of the cart is not very complex, but you have to put atention in the following points:

• To avoid problems soldering the pins of the socket in both sides, solder in the following order: IC3, IC2, IC4 and IC1.
• Don't forget to solder both sides were requiered. Some socket pins, C2,C1 and D1.
• Don't forget to solder the vias. Conections betwen both sides under IC1 socket.

How to get a Interface II ?

   If you haven't got neither a Interface II, nor a Interface II clone, you can get one following any of these methods:

• In an Auction in www.ebay.com.
• Making one by yourself. Belive me, it is dead easy. You only need to solder a few cables joining to conectors, is so easy that you can follow the instructions even in Spanish in this link: Como construir un Interface II”.

(Just connect the pins with the same name from the Spectrum expansion port to the Cart conector, that's all)

    How to create files for the ZX Flash Cart.

     Once you have your ZX-Flash cart, you need to program its Flash memory (29F040) with your favorites games. The final file you have to program in the memory flash, is the result of merge ten SNAs files and a menu program in a "special" way.

Fortunely we have counted with the help of Miguel A. García Prada, he has write a Windows program to make this task easy. Just select ten snapshots, push a buttom and get the final file to program the memory.

This program is available in the download area of this page. There is a page were Miguel A. share with us other things related with the Spectrum, as a Babaliba remake, visit Compiler Sofware .

Screen shot of the ZX Flash Creator.

If you have your own programmer (Willem,...) you can use the file obtained with the "ZX Flash Creator" to program the memory by yourself. If you have not a programmer, you can take this file to the electronic store and order a memory and a programmer service.

Questions and Answers

    Here you have the most frecuent questions and answers:

• When I press reset in the Interface II to change to a different game, its doesn't work.
  • It is normal, Once you have select a game you must power off /on the Spectrum to choose a new one. This is because the cart has a system to block the mapping when a game as been selected, and it needs a power off/on to be restored.
• When each program is started, I can see "trash" in the upper lines of the screen. It is normal ?
  • Yes. The procces to load the whole snapshot to RAM requiered some extra memory space. I use a part of the memory asigned to the screen to complete this process. This "trash" is a little routine to map and load the last ROM bank. Advice: use snapshot that change the screen just at startup, so these auwful lines will dissapear instantaniusly.
• Why the ZX Flash Creator has a test snapshot option?
  • When the snapshots are loaded to memory and run, the ROM available is the original with some minor differencies. This differencies would make that a program doesn't work. The ejecution under this test is close similar to the conditions the program will have in a real spectrum, so this way we can detect an incompatibility problem. Until now, all the program tested works, but obviusly, we can't test all the programs. NOTE: If you detect a program that doesn't work with this test, please, let me know.
• A part of the problem above... Could be snapshots that doesn't work in the ZXFlash cart?
  • I think that is very difficult, but it is posible that a snapshot use in the early moments of the startup, the memory area that I use to complete the RAM load. In others words, if a snapshot has been obtained under certain circustances could not work. For example: A snapshot obtained loading from a tape saved by interfece like Transtape 3, Disciple etc. that used a NMI to get a Snapshot. In this case you can run the program in an emulator for a few seconds, then save the snapshot again and it will work.
• In a cart with 512Kb could suit more that ten snapshot using .Z80 Format. Do you have a plan to implement this formats?
  • No. I know that compress formats like .Z80 would use the space much better than SNA format. For me ten snapshots are more than enough, if you are will to write in assembler a program to decompress Z80 files, you will count with all my help and support to implement this program in the ZXFlash cart.
• All the snapshots that I have are in .Z80 format. What can I do?
  • In www.worldofspectrum.org You can find converion programs to make this task. Or you can load the Z80 with an emulator and save as SNA.
• Do you have any plan to improve this proyect?
  • Yes. My plan is desing a very simple Flash memory/Flash carts programmer for PC. Thanks to it, the user could program by himself the memory several times without additional cost. ATENTION: This is only a plan, it is not a comitment, and it depend on the response of this proyect generate, and depend on my free time.
• Could ZXFlash cart be used to differents purposes?
  • Yes. You can program the first bank with your own operative system, and map the memory in banks of 16K. for your personal use. To do this would be better to get in contact with me for the details.
• I have been studing the circuit and I don't undersatand what is the function of D1.
  • When the cart is inserted in the Interface II connector, D1 join ROMCS and VCC with WR just like a jumper, but in a future, it will give us the possibility to plug the ZXFlash cart in a programmer directly, and re-program the memory without getting the memory from its socket.
• Are you going to sell ZXFlash carts? Can I order a ZX-Flash Cart?
  • No. If you want that I make a ZXFlash cart for you , with your favorites games, you must offer to me stuff related with home computers. Hardware related with the eighties computers.
• As a matter of curiosity How is the process of desing ?
  • It is very difficult that the hardware works at the first time, so I use very often preperfored boards in the develop period. "Foto prototipo". For the sofware I use intensively RealSpectrum emulator to debugg the assemebler code.    

     Downloads

 

ZXFlash-Diagram.pdf	Electronic circuit diagram in PDF Format.
ZXFlash-Circuit.pdf	The ZXFlash cart photomask in PDF Format
ZXFlash-Eagle.zip	ZXFlash Cart in Eagle format.
ZXFlash-Creator.zip	Program to create ROMs with ten SNAs. (C) Miguel A. Prada V 1.0
ZXFlash-Source.zip	Source in assembler of the control program of the cart.
VBRUN60SP5.EXE	Only needed for Win95/98. Just run to install VBRUN60.DLL on your system

News :

15 de Mayo 2005

Proyect complete, first version publicated.

18 de Mayo 2005

Added VBRUN60SP5.EXE in order to use ZXFlash-Creator under Windows 95/98.

    Thanks to :

    Jose Leandro. Autor of amazing desings related with Spectrum (visit Los Trastos de Jose Leandro ) His great project "Super cartucho Interface II" has been an inspiration for me, and push me to make a old dream come true, the ZXFlash cart. And thanks for your help fixing the problem with my GalBlast programmer. Now that I have a GALs programmer working, I have a new vision for many projects.

José Manuel (The WebMaster) Without his help and support this page would not exist. And for his help buying in ebay...

Miguel A. Prada. The programmer of the "ZXFlash Creator" . His great contribution was fundamental in this project. And thanks for keep the spirit of the Spectrum alive from his colaborations with online magazines and from his page.

To María Jesús, and my daughters Andrea and Inés, for their infinte patiens with this mad lover of old computers. I love you.

     Madrid May 15th 2005

     Disclaimer

   I share the information here without any warranty nor responsability for the damages it could cause to your computer.

What I can tell you is that "IT WORKS !!!" but .... up to you.

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