Monthly Archives: January 2017

Zilog z80 to Motorola 6809 Transcode – Part 013 – Sprites and more RAM!

First I have to give a big thanks to Mark McDougall who explained to me that I don’t have to have the video ram in the main 64k of addressable space the CoCo3 uses!  I should have realized this myself since working … Continue reading

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Zilog z80 to Motorola 6809 Transcode – Part 012 – Pacman is in the building and handling the z80 RLCA instruction

I’ve started implementing sprites and I’ve got the red ghost animating and Pac man moon walking a little across the screen.  You can’t see it from the picture below but you can see that I finally have Pac Man on … Continue reading

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Zilog z80 to Motorola 6809 Transcode – Part 011 – Pacman Maze on screen

Not much to report on, I’m still trying to figure out how the sprites get loaded in Pac Man and how to best implement my sprite engine with it.  While going through some more code I decided it would be … Continue reading

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Zilog z80 to Motorola 6809 Transcode – Part 010 – Fixed IRQ interfering with character rendering

Well I figured out the problem with the characters not being displayed correctly.  It was a problem with the Interrupt.  While in regular mode the code was displaying the text characters and at the same time the IRQ would print … Continue reading

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Zilog z80 to Motorola 6809 Transcode – Part 009 – Ghosts on screen and some z80 transcode tips

A little more progress…  I still have to make the other coloured ghosts but at least I know where in the code it draws these ghosts so it should be relatively easy to draw the correct one at the correct … Continue reading

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Zilog z80 to Motorola 6809 Transcode – Part 008 – Character generator fixes and has Colour support

I fixed up the DrawCharacter routine that now masks off the high bit of the screen address as some of the pointers were pointing to addresses in the C3D4 range which is not possible.  I also added a routine that … Continue reading

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Zilog z80 to Motorola 6809 Transcode – Part 007 – Character display is working

I’ve made more progress over the last few days…  I have Pac Man text characters working and it runs as far as the test grid now all being displayed properly…  I’ve decided to not keep the original ROMS in their … Continue reading

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