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I plan to develop a mezzanine PCB intended to sit in place of two ICs in an existing circuit and replace their function. Height is limited as the device is only 1U high in total.

One of the original ICs is a 28 pin 0.6" DIP 8kB SRAM, and the other is a 16 pin 0.3" DIP 74HC138 which acts as an address decoder. My intent is to replace the 8kB RAM with a 32kB RAM and a GAL to act as an improved address decoder.

What would be the most appropriate connectors to use for the connection between the two boards ideally such that I can simply remove the board and re-insert the original ICs if desired? The existing ICs are not currently socketed. There's enough space available that I don't need to use the footprint of any such connectors to hold components.

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    \$\begingroup\$ Please show a picture of the PCB, with annotations. \$\endgroup\$
    – Fredled
    Sep 17, 2020 at 23:21
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    \$\begingroup\$ hm, that sounds like you could just drop in a modern microcontroller (>=100 MHz!) to emulate both decoder and RAM) \$\endgroup\$ Sep 18, 2020 at 6:54
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    \$\begingroup\$ @MarcusMüller that would be massive overkill - I only need an 80 cent GAL and a single RAM chip. Using a microcontroller instead would at the very least need a bunch of passives, a xtal, firmware, and most likely the need to bidirectionally convert voltage levels too (the original system is 5V). \$\endgroup\$
    – Alnitak
    Sep 18, 2020 at 8:01
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    \$\begingroup\$ @Alnitak nope, a modern microcontroller comes with an on-chip oscillator, and typically needs one or two decoupling caps; so that's less components than your solution, at a lower cost. There's 5V capable MCUs for the automotive market, and 80ct isn't that cheap - and writing a MCU firmware sounds easier to me than designing the GAL configuration (but that's personal preference). \$\endgroup\$ Sep 18, 2020 at 8:02
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    \$\begingroup\$ @Alnitak ah interesting! Yeah, but then you can have the same with a microcontroller. \$\endgroup\$ Sep 18, 2020 at 8:11

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I found another similar question which suggested looking for "DIP headers", which has led me to the CnC Tech 200 series of thru-hole M-M DIP adapters.

These have turned pins which will be suitable for plugging into IC sockets installed on the main PCB.

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  • \$\begingroup\$ part link for reference - arrow.com/en/products/220-1-28-006/cnc-tech-llc \$\endgroup\$
    – Alnitak
    Sep 19, 2020 at 12:33
  • \$\begingroup\$ DIP header, strip header, etc. Or, a wire-wrap socket on the mezz. What is the total height above board you have to work with? (1U minus pcb standoffs minus pcb thickness minus mounting frame / packaging minus clearance above the mezz board) \$\endgroup\$
    – AnalogKid
    Sep 19, 2020 at 13:16
  • \$\begingroup\$ AND, what is the minimum RAM write-cycle time in your application? \$\endgroup\$
    – AnalogKid
    Sep 19, 2020 at 13:18

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