README.TXT file for EPROM PROGRAMMER.›››This file describes an EPROM›PROGRAMMER for the ATARI XL›computer, which programs 8 and 16›kBytes EPROMs.››CAUTION:›Building this device will require›advanced soldering skills. Note that›I will not be liable for any damage›that may occur to your ATARI or any›other device.››ALSO NOTE that this project is›shareware. It is available on an›'as is' basis. Although you can›write to me, I cannot quarantee that›I will be able to provide you with›solutions or answers to problems you›might encounter.››Rudolf Cornelissen.›››››The programmer is a cartridge which›is placed in the game connector on›the top of the XL computer. It needs›no external power sypply. It does›need an ATARI with at least 40k of›RAM.››The files contained here are:››-PGM.BAS     : This is the BASIC›               program which›               interfaces with the›               programmer;›-RUDPROG2.PCB: This is the hardware›               layout: double sided›               PCB with silkscreen.›               This file was made›               with smARTWORK from›               WINTEK on the PC.›-RPSOLCOM.PCB: This is also the›               hardware layout, this›               time made on the›               ATARI itself with›               smARTWORX (shareware).›               It contains only the›               two copper layers.›-RPSOLSIL.PCB: This again is also›               the hardware layout,›               this time only the›               solder layer and the›               silkscreen.›               NOTE that this silk-›                    screen contains›                    all components›                    and their values!›-README.TXT  : This text file.›››Building the hardware:›You will have to make a double sided›printed circuit board. You can›connect both layers with short wires›thru the board, sometimes component›leads are also used for this purpose.››The board can be built in an orderly›fashion in this way.››The best thing you can do is to make›the print from the PC layout file.›It can also be done from the ATARI›files, but make sure that the›connector is lengtened with 2.54mm!›(see ATARI layout files.)›You will need the ATARI SOLSIL file›to know where to put the components›and what values they have.››››Here are some tips about the system:››- Be ware to place EPROMs with pin 1›  pointing to the TL497 chip, not›  the other way around. Failing to›  do so might result in defects in›  the EPROM, programmer, ATARI or›  ATARI power supply!››- Also be ware not to try to program›  an EPROM at 21V when it was made›  for 12.5V! This will most likely›  destroy the EPROM.›  If you are unsure of the correct›  voltage, first try 12.5V. If this›  doesn't succeed (and the EPROM was›  REALLY empty), then try 21V. NEVER›  the other way around!››- USE 2Mhz versions of the PIAS!›  Although it might be possible to›  get the system working with›  1.5Mhz devices (My system did).››- Because of the step-up power supply›  on the programmer, there will most›  likely be some minor flickering›  effects visible on your screen.›  This is normal, so don't worry.››- NOTE that the inner multiturn›  resistive potentiometer should be›  set for the 12.5V programming›  voltage, while the outer one has›  to be set for the 21.0V voltage.››  If the programmer is placed and›  it's software is started, the›  programmer will generate 12.5V.›  (If adjusted properly.)›  You can measure this voltage›  across the 1000uF capacitor on top›  of the programmer.››  The 21.0V setting can be adjusted›  when you select a 21.0V program-›  ming voltage and then give the›  'program' command with no EPROM›  inserted. During the first 30›  seconds, the programmer will wait›  for this voltage to stabilize,›  before actually starting the›  program routine.›  During this time, you can set›  this voltage to the correct value.›  (If 30 seconds isn't enough, just›   retry. In the end you will get it›   right.)››- If you use the ATARI layout files›  be sure to lengten the connector›  with 2.54mm!! (see layout files)››- The program is written in BASIC,›  but the actual programmer inter-›  face is written in machine›  language. I use it with DOS 2.5›  with no RS232C drivers loaded.›  On a system running in this›  fashion, there will be about›  3.5kBytes spare RAM available›  for program extensions (or a›  bigger DOS system), before using›  the programmer will overwrite›  it's BASIC listing. If overwriting›  happens, the system will crash›  of course!›  Make sure the memory starting at›  decimal location 20000 and above›  remains unused as this memory is›  used as the EPROMs RAM buffer!!!.››- The program's 'load', 'save' and ›  'dir' routines are written in›  BASIC. They would run much quicker›  if they would be written in›  machine language. Also these›  routines are currently not 100%›  'fool-prove'.›  The rest of the program is in›  'optimal condition', to my›  knowledge.›  The reason why the load/save/dir›  routines aren't, is that I never›  found the time to finalize them.›  (If someone likes to optimize›   this, please do.)››››That's all there is.››Good luck if you are going to build›one.›››Rudolf Cornelissen (1/1999)››Email:›R.Cornelissen@SynSpec.NL›