Introduction

EPROM Programmers are now software controlled. This works well if the chip type and footprint is in the database but what happens when a variation is required?

Connecting Memory chips in parallel to expand the overall memory size is a common requirement.

This break out card addresses both these applications. Firstly it allows the user to set in hardware, a source footprint to be translated into a target footprint, using either switches, jumpers or jumper leads. Larger memory devices that are not be supported may also be programmed, by manually setting the most significant bit individual address signal lines to a 1 or 0 using the tri-state switches provided. This allows larger devices to be programmed in several steps using a 32 pin programmer. In some cases the physical chip or the footprint is not available. The user may know, for example, which signals need to be swapped, changed or held at a different logic level and would welcome a board to try different combinations before the final solution is found, either be theory or by trail and error.

• The source 48/40/32 pin

• headers 
  fit into the ZIF socket of the EPROM programmer. They may be fitted at either a 0.3" or 0.6" pitch.

• The target 50 way connector allows a plug and socket to be used. 
  
  Space is also provided for 

• 32 pin
• 40 pin
• 48 pin

size ZIF sockets if required. 

Additional tri-state switches are provided to take up the job that some adapters do holding chip select pins, for example, when the number of active pins from the programmer is at a premium.

In the case of some older 8-bit game computers and the Z88 card for example, the flash or EPROM chip is inside a plug-able module. The address and data lines are then only available via a bespoke connector. 

Secondly four multiple memory chips may be connected together. The spacing of the sockets and headers allow either a 0.6" or 0.3" pitch devices tp be paralleled up together. A decoder chip layout is also provided.

Object

of this card is to design a PCB that can be used in a variety of ways depending which components are fitted This allows the user to have full hardware control of the signals by selecting switches for testing, or making permanent changes by using wired links.

The lever that grips the chip can either be at the top left-hand side or the bottom right-hand side of the ZIF socket. The L shaped card is designed so that it does not fowl this leversource header at a 0.3" or 0.6" pitch may be fitted on the left or right-hand side of the board allowing both types of EPROM erasers to be used.

Design

The design of the card is split in 3 parts where the first and last parts are similar and the middle part translates the desired signals.

Source - plugs into the EPROM Programmer

Signal Box - switches individual signals using DIP switches and jumpers 

Target - ZIF socket or connector plugs into the target device

Source - Plug to fit into the ZIF socket of the EPROM programmer

• Address Tri-state switches
• Header for additional address lines for Willeim programmers
• Space for 2 off 24 pin headers to be used for 48 pin programmers.
  Shorter lengths may be fitted for the smaller sizes of programmers.
• Headers may be placed at 0.6" or 0.3" pitch.
• These headers are repeated if required for jumper wires are to be used to connect directly to the outputtarget.
• Tracks are marked with a section that allows them to be permanently cut.
• Another row of headers if required, may be fitted the other side of these cuts, so that the tracks may be reconnected using header links.

Signal Box

• Address decoder chip
• 2 x 12 way DIP switches to and headers with links to select the footprint for the source and destination devices
• Tri-state switches to statically select the state of individual pins e.g. Chip Select unsupported address lines.

Target - 48 pin ZIF Socket - Additional connector

• This allows up to the a maximum size 48 pin zif socket to be used.
• Sockets may be 0.6" or 0.The headers are repeated so that jumper wires may be used3" pitch.
• Headers are repeated if required for jumper wires to be used to connect directly to the source.
• Tracks are marked with a section that allows them to be permanently be cut.
• Tracks Another row of headers if required, may be fitted the other side of these cuts, so that the tracks may be reconnected using a header linklinks.
• 50 pin IDC connector to connector (2 row 0.1" pitch footprint) to allow connection to daughter boards, non standard external cards or wiring looms using an IDC plug and socket.
• Z88 external card socket connector

Parts List

CONNECTOR, HEADER, THT, 2.54MM, 50WAY

109-6994 

HEADER, S/LATCH, STR, 2.54MM, 50WAY

221-5272

SOCKET IC, ZIF, 48WAY

HEADER, 2.54MM, THT VERT, 24WAY

CRIMP LEAD, SKT, MICRO-FIT, 150MM

JUMPER SOCKET, BLACK, 2.54MM, 2WAY

HEADER, VERTICAL, 0.1", 8WAY

588-775

HOUSING, 26AWG, 8WAY

109-8717

RIBBON CABLE, IDT, 8WAY

SWITCH, DIL, SLIDE, 12WAY

947-9090

SWITCH, DIL, TRI-STATE, 10WAY

152-2013

RESISTOR, CARBON FILM, 2K2, 0.25W, 5%

933-9302

SN74LS139AN - IC, DECODER/DEMUX, 74LS139

959-2296