Thursday, January 24, 2013
Sunday, November 18, 2012
Permanent memory at this time was a Programmable Read Only Memory chip. The first generation was not erasable. You programmed a memory location by using very short pulses of higher-than-normal voltage to blow fuseable links inside the chip. Hence the term “burning.”
If you made a mistake, there was no “undo” or “real easy” way to fix it. The not-so-cheap chip was now trash and you had to start over. Thus, burning a PROM was a task done in a careful, slow and deliberate fashion – with no one else at home and the phone off the hook.
An alternate approach, for a small bit of code, was to populate a board with 1N48, 1N914 or similar diodes, to create your own PROM. If a diode was soldered in, the bit was a “1.” If the connection point was open, the bit was “0.”
Some early CW ID encoders for RTTY and repeaters - many still working today - used such schemes, as well. - WA3UVV
Thursday, November 1, 2012
You're invited to take the November 2012 WRO Reader Survey online. Click here to be linked to the questionnaire. It takes only a few minutes and will help us to better bring you content that is relevant and entertaining. Thanks.
- Richard Fisher, KI6SN
Editor, WorldRadio Online