DEQNA Ethernet Interface: Part I

The last few days I've been trying to get the DEQNA Ethernet card working on the PDP-11/23. I'm hoping to be able to use this to transfer data from other systems more quickly than via the serial port. Unlike most modules, it's not simply a case of plugging in the card and setting up the appropriate driver software. The DEQNA contains its own boot code which needs to be executed at start-up to initialise the card. This is usually done automatically by the system's own boot ROMs but, since the system was upgraded with the KDJ11-A processor and MXV11-B, this code is no longer present. My plan is therefore to locate the appropriate boot code and run this manually before booting an OS.

First job was of course to find the code required to load and execute the DEQNA's boot code. It is of course feasible to write this from scratch, but I'm not one for reinventing the wheel. Although I didn't find the code straight away by searching the web, I knew from micronote 15 which ROMs contained the required code. I was also able to find images of these on the web which I then disassembled for examination. Unfortunately there was no mention of the DEQNA's CSR address in any of these, so finding the code wasn't going to be as easy as I'd thought...

Thankfully, a USENET archive search turned up a post featuring example boot code with which I was able to locate similar code in the ROM image. I'm now in the process of using these examples to write my own program that can be ODT-ed in when the system starts up.

[The link below will take you to the next chronological step in the project. However, the final part of the DEQNA story, featuring the working bootstrap is now available here.]

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