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Old 9th Aug 2018, 10:29 am   #47
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
Default Re: Tesla MH74S571 programming.

Quote:
Originally Posted by kazzawozza View Post
Hi Sirius,

As it happens, a (DM74S571) PROM and EPROM programmer was manufactured for the Acorn System range, and a circuit diagram exists (https://www.4corn.co.uk/archive/diag...Programmer.jpg) but I don't know of any surviving software to go with it.
Unfortunately what works for the DM74S571 does not work for the MH devices, as you will have gathered by now.

On the DM devices the bit to be programmed is programmed by raising the IC's VCC to 10.5V and then zapping the bit to be programmed with VPP (10.5V)

On the MH devices it seems the bit to be programmed has to be held at 0V and the other bits held high (5V) via 3K9 resistors. Then the IC's VCC has to be raised from 5V to 10.5V for a period of time (ie, the length of the programming pulse).

So hardware designs for DM74S571 programmers just don't apply to the MH74S571.

The other major difference between the devices is the length of the programming pulses, which on the MH74S571 are dynamically increased in length from an initial 1ms up to as long as 20ms with the bit being verified (read) after each attempt to see if it has programmed yet.
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