General Category > LisaList2

Corvus HDDs and the Lisa

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jamesdenton:
Ok, I've got the Saleae on there and here's what I'm seeing as the default state:

RESET - HI
READY - HI
STROBE - HI
DIRC - LO

When attempting to create the filesystem, here's what we see:



Here's an example of a working(?) handshake:



Will continue to play around.

sigma7:

--- Quote from: jamesdenton on March 24, 2025, 04:52:56 pm ---When attempting to create the filesystem, here's what we see:
(reset pulses low twice)

--- End quote ---

This doesn't make sense to me... if RESET going low is the first thing to happen, then the Lisa must be driving it.

a) To drive RESET low, PB7 must be set low. I don't see this in the bits of code I found.
and
b) According to the Corvus schematics I've looked at (maybe not the one that is applicable to your device), RESET is an output. If that's the case for your device, then the Lisa wouldn't be trying to drive RESET low.

So, I'm guessing some options are: some important code is hidden somewhere else, or I didn't find the appropriate schematic, or there is a wiring error, or I'm missing something obvious, etc.

sigma7:

--- Quote from: jamesdenton on March 24, 2025, 04:52:56 pm ---an example of a working(?) handshake

--- End quote ---

I think you need to connect the data bus, so when the bus direction turns around and the Lisa reads the status byte from the Corvus, you can see what code it is returning.

jamesdenton:

--- Quote from: sigma7 on March 24, 2025, 05:36:08 pm ---
--- Quote from: jamesdenton on March 24, 2025, 04:52:56 pm ---an example of a working(?) handshake

--- End quote ---

I think you need to connect the data bus, so when the bus direction turns around and the Lisa reads the status byte from the Corvus, you can see what code it is returning.

--- End quote ---

I will work on refactoring my adapter to make it easier to debug. My logic analyzer only has 8 channels, so this might take a few attempts.


--- Quote ---(reset pulses low twice)

--- End quote ---

I am wondering if RESET on the Corvus should not be tied to RESET on the Lisa, but perhaps something else? There's an adapter here https://bitsavers.trailing-edge.com/pdf/corvus/flat_cable_interfaces/mnaberez_flat_cable_experiments/pictures/ showing RESET wired up to one of the IDC16 connectors, and a reference to it at https://github.com/mnaberez/corvus/blob/main/corvus/client.py#L15. Maybe the Lisa is driving it LO and I just need to wire it HI to avoid an unintentional reset?

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