Volume 2, Number 4 – September 1982

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  1. Short out the pulse capacitor, C10, from the old 2708 25 volt pulse circuit showy on sheet 3 of the circuit diagrams. Take a lead from ‘A” of that diagram (I used the end of R5 furthest from TR2) to pin 3 of switch 2. This will provide 25 volts on pin 20 of the recipient EPROM.
  2. Lift IC 2. Bend out pins 7 and 14. Use one of your two 1 Meg resistors to pull pin 7 down to 0 volts by connecting it between pin 7 and the wide track close to pin 7. Pin 7 must also be connected to Bit 6 of port 5. This is easiest done by using the through-plated hole next to the C7 legend. Pin 14 is left unconnected. Bit 6 of port 5 now controls a 25 volt/​0 volt output to pin 20 of the recipient EPROM.
  3. Connect together pins 8 and 9 of switch 2 to put A10 on pin 19 of both EPROM.
  4. Fortunately, IC 3 produces an All signal on pin 1. I bent pin 1 of IC’3 out and connected it to pin 11 of the same switch to provide All on pin 21 of both the donor and recipient EPROMs.
  5. Join Bit 2 of port 5 to pin 6 of switch 2. This is best achieved by using the plated hole just by the TR6 legend and close to the switch. I also pulled pin 6 of the switch to 5 volts with the second 1 Meg resistor. I used the legend end of R20 for my 5 volts.

Your board is now a 2732 programmer when switch 2 is pushed in and a 2716 programmer when switch 2 is out, but only when the software is correct.

Software Modifications.

Thank you Bits and PCs for your fully documented listing. I am most grateful. First, the functions of the bits 0 to 6 of the control word that is used to control the EPROM blower.

00 voltsIncrements address counter clockACLOCK
05 voltsNo increment
10 voltsEnables address counter clockRESET
15 voltsResets address counter clock
20 volts2732 programming pulse of 0vRP2732
25 volts2732 standby, 5v on​/CE
30 voltsEnables donor ROM /OEMROM
35 voltsDisables donor ROM
40 voltsDisables 2716 5v programming pulseTRIG
45 voltsTriggers 2716 5v programming pulse
50 voltsEnables 2716 receptor ROM /OERW2716
55 voltsDisables 2716 output from /OE
60 voltsRead enable 2732, 0v to /OE VppV2STRG
65 volts25 volts to 2732, 25v to /0E Vpp

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