Electronic Keys & Locks

1-Mbit Adapter For EPROM Programmer Schematic Circuit Diagram

EPROM Adapter for 27C1001 with 64 Kbyte x 2 Programming Steps

This adapter facilitates the programming of the 27C1001 EPROM, boasting a 1-bit capacity organized as 128 Kbyte x 8. To utilize this adapter, your EPROM programmer must support the programming of 512-bit EPROMs, such as the 27512 or 27C512 (64-bit x 8). The adapter follows a two-step programming approach for the 27C1001, processing 64 Kbyte at a time, and seamlessly fits into the 28-way (or 40-way) ZIF socket on your EPROM programmer. Manual selection of the 64-byte block is achieved with the help of a switch.

The adapter’s circuitry comes with some interesting features. Socket 1 establishes the connection between the adapter and the EPROM programmer, while socket 2 accommodates the 27C1001. The PGM input of the 27C1001 is triggered (i.e., set to logic low) when the programming voltage, Vpp, on socket 1 surpasses the zener voltage of D4, and the CS on socket 1 is kept low by the programmer. The zener diode also enables the programming voltage (12.5 V) to pull the “OE” terminal of the 27C1001 high, allowing the device to be programmed. The VPP input of the 27C1001 is maintained either at +5 V (during reading operations) or around +12 V (during programming). To ensure a sufficiently high operating voltage (nominally 5 V) for the 27C1001, a Schottky diode of type BAT85 is employed in position D2, marked by a forward drop of only 0.2 V.

1-Mbit adaptor for EPROM programmer Schematic diagram

EPROM Adapter Construction for Address Selection

For address selection, switch S1 manipulates the highest address input, A16, of the 27C1001, toggling it between low and high to choose between the lower and higher 64 Kbyte blocks in the device (A16 = low and A16 = high, respectively). The illumination of diode D5 signifies the addressing of the lower block.

The construction details of the adapter are evident in the PCB layout. Begin by installing the single-wire link on the board. Socket 1, comprised of two 14-pin PCB pin headers, is positioned on the track side of the board. Switch S1 is a self-locking push-button from My with a built-in LED indicator. The PCB is designed to accommodate both 28-way and 40-way ZIF sockets.

1-Mbit adaptor for EPROM programmer Schematic diagram

Parts list

Resistors:
  • R1 = 10 kΩ
  • R2 = 1 0 kΩ
  • R3 = l 00 kΩ
  • R4 = 1 kΩ
  • R5 = 100 kΩ
Capacitors:
  • C1, C2 = 100 nF
  • C3 = 1 nF
Semiconductors:
  • DI = zener, 5.6 V, 400 mW
  • D2 = BAT85
  • D3 = 1N4148
  • D4 = zener, 8.2 V, 400 mW
  • D5 = LED 3 mm
Integrated circuits
  • ICI = 741-ICTOO
Miscellaneous:
  • S1 = self-locking push-button switch with integral LED
  • 2 off 14-way strips of PCB pins (long pins at one side)

1-Mbit adaptor for EPROM programmer Schematic diagram

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