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EPROM Emulator

a perfect imitation-EPROM

EPROM Emulator
As opposed to most other EPROM emulators, the design discussed in this article provides a virtually perfect imitation of a ‘real-life’ 27C256 device, which may be programmed in any programmer as well as inserted into the target system.An EPROM emulator is a useful if not indispensable tool if you are into developing software for a system employing an EPROM for storage of executable code or fixed data. Such a ‘programmable imitation EPROM’ obviates the need to erase an EPROM after any programming cycle, before the new (and hopefully improved) program may be loaded into the chip. Erasing an EPROM with the aid of UV light usually takes about 20 minutes, which, many of you will agree, is an annoyingly long time.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Resistors:
R1,R2,R5,R6 = 10k?
R3 = 33?
R4 = 100?
R7,R8 = 1k?2
R9 = 8-way SIL array 10k?
Capacitors:
C1-C4 = 100nF
Semiconductors:
D1 = zener diode 7.5V
D2,D3 = zener diode 4.7V
D4 = LED, high-efficiency, yellow
D5 = LED, high-efficiency, red
T1 = BS170 or BS107
IC1 = 78L05
IC3 = 62256-70CP
IC4 = GAL 16V89, programmed, order code 024066-31
IC5 = 74HCT245
Miscellaneous:
IC2 = 2 ? 14-way pinheader
S1,S2 = pushbutton
K1 = 9V battery clip with leads
PCB, order code 024066-1
Disk, GAL JEDEC listing, order code 024066-11
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