DEQNA Ethernet Interface: Part II

I finally got round to sitting down with the bootstrap code I'd found before and figuring out how to boot the DEQNA by hand. The example code was successfully assembled after making a couple of minor adjustments to suit the syntax of the assembler. I also removed the first few instructions for selecting the first or second DEQNA. The code below will boot the first unit but the second can be booted by setting the address at location 10002 to 174460. Probably not the most efficiently written bootstrap ever, but it gets the job done!

0010000: 012701 174440 012761 000002 000016 022761 010062 000016
0010020: 001066 005061 000016 012703 002000 010304 012724 100000
0010040: 011324 005024 012724 177400 005024 005024 011324 012714
0010060: 020000 010361 000004 005061 000006 012761 001010 000016
0010100: 005000 077001 042761 000010 000016 005000 077001 012761
0010120: 000002 000016 005061 000016 012704 002014 042714 037777
0010140: 022714 140000 001014 022737 000240 000000 001010 122737
0010160: 000001 000003 001004 012700 000000 000137 000000 000000
0010200: 000776

The only modification I needed to make was at address 10014. This value is used to check the value of the CSR after a reset and, if it doesn't match, the bootstrap will bail out. The original value was 000062, but testing showed the DEQNA was responding with 010062. This isn't really all that surprising as the "1" indicates that the fuse is present in the bulkhead and therefore the transceiver is getting power. You could, of course, remove this check (and the others) to shorten the program, although it will make it more difficult to figure out what's happening if/when things go wrong.

When the code is done, all the LEDs on the back of the DEQNA should go out to indicate the interface is initialised. At first, LED 3 stayed on, but that was just the DEQNA's way of reminding me I needed to connect the bulkhead cable... As it is, the code will just loop when it's done. This isn't a problem because you can freely halt and reset the machine after the card is set up.

I've got hold of a AUI transceiver off of eBay with which I can connect the DEQNA to my existing UTP-based network. Not only does this save me from having to set up a thick Ethernet segment just to hook up one PDP-11, the DEQNA must have the transceiver (or a loopback adapter) connected in order to boot properly. With the tranceiver, I was even able to run the XXDP diagnostic, ZQNA. All tests checked out fine, so I'm confident the PDP-11 will be speaking Ethernet soon; that is, when I configure an OS to make use of it. I'm not having too much luck building a 2.11BSD kernel with network support as it doesn't want to link. Hopefully that will be sorted soon.

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