USB Programmer for EPROM 27C, (27C256, 27C512, etc.)

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The programmer needs to be configured for whatever type of EPROM you are using. The Willem requires you to set jumpers and dip switches whereas my TOP 853 allows chip selection from software. In particular make sure the Vpp is correct and that the IC is oriented correctly and in the right position on the IC holder.

From time to time those of us with the passion to preserve ancient computers from the 1970 and 1980s will come across the need to replace a failed masked ROM or EPROM. This article is for those that are unfamiliar with EPROMS and want to get their machines up and running again. The text below covers only EPROMs rather than the later programmable ICs such as EEPROM, MPU, GAL/PLD etc. mostly because I don't know much about them. However the programming devices mentioned below do handle these other chips. Furthermore, the article doesn't cover all of the theory and physics. Rather it provides enough practical tips and information for readers to attempt an EPROM replacement of failed compatible parts. I dont know if I should just make it on veroboard as it was in the beebug magazine and see what happens. I thought I'd make a PCB that way I could reduce the size a bit and out it in a small case. But alas, it wasn't to be. I'm not sure if there's a problem on my printer port / user port or both. EPROMS then, are ideal for replacing mask ROMs that have gone bad along with adding extra applications and utilities, and for general tinkering. Early "Stored-Program" type computers — such as desk calculators and keyboard interpreters — began using ROM in the form of Diode Matrix ROM. This was memory made up of discrete semiconductor diodes placed on a specially organized PCB. This gave way to Mask ROM with the advent of integrated circuits. Mask ROM was a lot like Diode Matrix ROM only it was implemented on a much smaller scale. This meant, however, that you couldn't just move a couple of diodes around with a soldering iron and reprogram it. Mask ROM had to be programmed by the manufacturer and was thereafter not alterable.Read-only memory (ROM and PROM) refers to modules designed for the long-term storage of information that does not change dynamically

We can now turn to the software. I’ve made a fair few changes to the original software, largely to improve performance and remove redundancy.

These EPROMs are NOT in mission-critical equipment. And although I used to regularly do this for customers oh, so many years ago, I want to give the customer the best chance these chips will work correctly for the indefinite future.

I’ve also seen people use opto-isolators to drive Vpp pins too. Not an approach I’d use, but it definitely does work. USB powered universal 48-pin chip programmer with compact dimensions and minimal weight. Dataman S6 can program without the need for a family-specific module, giving you the freedom to choose the optimal device for your design...Since I’ve already written code to write to a chip with software data protection via a Z80 I thought it would be helpful to update my own ‘BenPrommer’ to handle the 28C256 and to document both the hardware and software changes needed. Hardware Changes I’m looking for VVDI PROG from xHorse and I like this tool, I think this tool is more better than XPROG and the original XPROG is around 850€ and original xHorse is around 430€ Before we get into the hookup it's probably a good idea to familiarize ourselves with EEPROM and the history of ROM in general. That said, if you don't nerd-out on computer history it's probably safe to skip that section. What is ROM? Erasure of the EPROM begins to occur with wavelengths shorter than 400 nm. Exposure time for sunlight of one week or three years for room fluorescent lighting may cause erasure. The recommended erasure procedure is exposure to UV light at 253.7nm of at least 15 Ws/cm 2, usually achieved in 20 to 30 minutes with the lamp at a distance of about 2.5cm. [9] When constructing as a 270x/TMS2716 programmer, only the following components can be omitted: J1, SW1, U3, C4, C5, C6, C7, C8, R19.