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Testing the microcode

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James Stormes edited this page Dec 31, 2020 · 10 revisions

It was time to test the microcode. With the 25.175MHz oscillator in place and the 640x480at60_25.175MHz.bin code loaded into the PROM. I measured the timings.

Part Expected Measured
Visible area 25.422045680238 µs 25.417 µs
H Sync pulse 3.8133068520357 µs 3.833 µs
V Sync pulse 0.063555114200596 ms 0.063583 ms
Full Frame 60 Hz 59.922 Hz

Next I attached a 725 Ohm resistor to the Visible area pin and connected that to the blue VGA signal pin (pin 2), and grounded the other colors. I attached v-sync and h-sync to the appropriate pins (v-sync is pin 14 h-sync is 13), then grounded all the other appropriate VGA pins.

Testing circuit connected to VGA

First VGA monitor Sync

VGA Testing schematic 1

Introduction
A Fast Counter
Testing the Counter
Slowing down the Count
Programmable Counter A
Programmable Counter B
Not Quite a Computer (NQC)
A Program to write the Microcode
Testing the microcode
VGA Test #2
8 Bit VGA Slice
8 Bit VGA Dice
Glyphs AKA Character ROM
More Success Than Expected
8 Bit Slice and Dice

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