An Innovative Solution to an Old Problem

UV-Erasable PROMs

With nearly 20 man-years experience in the field of Embedded Microprocessors, we well remember the days when changing firmware involved erasing an EPROM for 20 minutes in a UV eraser, programming it in a PROM programmer, and finally plugging the EPROM into the target board. During development & debugging this would soon become very tedious!

With the advent of electrically-erasable PROMs, the UV eraser could be dispensed with. By removing the need for a quartz window to admit UV light, the expensive ceramic package was no longer needed and cheap plastic encapsulation could be used instead.

With Flash EPROMs and In-System Programming (ISP), today even the PROM programmer is largely redundant.

But even Flash does still have its limitations when developing & debugging embedded code:

The Triscend E5 offers an escape from these limitations:

The JTAG interface, together with the extreme flexibility of the E5's memory architecture, allows in-circuit code download & program execution from the internal SRAM, an external SRAM, or an external Flash device.

In developing the new GSM STU, Versus Technology took advantage of these features by modifying some prototype boards to replace the normal Flash socket with an SRAM.

Off-the-shelf pinout adaptors were used to mate the SOJ-packaged SRAM to the PLCC socket site (click the photo for a larger image).

Triscend E5 with Flash replaced by SRAM.

While this adaptation greatly enhances development & debugging by removing the inconveniences noted above, there are still some limitations; eg:

Custom Flash-replacement SRAM modules

In response to these issues, Antronics Ltd conceived the idea of a custom Flash-replacement SRAM module that would simply plug into the standard Flash socket.

Detailed design was completed by Versus Technology, and modules were produced by Winslow ADAPTICs.



These modules have proved a great success, and have been used in several subsequent development projects:

A Custom Flash-replacement SRAM module in use

A pair of Custom Flash-replacement SRAM modules in use

A Custom Flash-replacement SRAM module in use


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