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Paul Bleisch

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November 2010

Debugging stuck bits

I’ve been blocked on making progress on the retro pc project due to bad reads from the ROM. The seemingly simple snippet of boot code should light an led wired to to the i/o ports (any port).

section .text
resb 0x7F0
org 0x7F0

start:
mov al, 0x1

 

again:
out 0x10, al
jmp again

When assembled, this turns into the following x86 bits:

00007f0: b0 01 e6 10 eb fc

Unfortunately, when I tried to boot the bundle of wires on the breadboard, I got the following while looking at AD[0:7] on the 8088.

00007f0: b0 01 e2 10 ...

Continue reading “Debugging stuck bits”

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Using Ultrascope for Rigol DS1052E

I’ve become more and more annoyed at having to export images from my Rigol scope to a flash drive plugged into the device. I’d much prefer to capture signals and images directly from my Macbook. Unfortunately, the PC software that comes with the Rigol — Ultrascope — does not run on Mac OS X. Boo. Over the last couple nights, I’ve played with the idea of writing a Cocoa app to pull data from the scope. USBTMC + Cocoa seems like a pretty good path to go.

Continue reading “Using Ultrascope for Rigol DS1052E”

Sometimes it is a bad part… sometimes.

I’ve spent the last few weeks working on my retro pc project. The first step with the 8284 seemed to go well but the┬átrouble began when I tried wiring up the 8088. I wasn’t getting anything remotely close to the expected boot sequence. According to the datasheet and
The 8088 Project Book
a few clocks after dropping RESET back to zero, the 8088 should raise ALE after placing 0xFFFF0 on the address lines.

No such luck.

Continue reading “Sometimes it is a bad part… sometimes.”

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