How do I redefine characters with 8k or more RAM?
Posted: Mon Jan 01, 2024 2:38 pm
Good evening.
I am learning how to redefine characters and print them on the screen to make "mostly" full screen images. I can do it just fine for the stock system and with the 3k RAM expansion installed. It would seem that the process is not the same when using an 8k or higher RAM expansion. I'm not entirely sure exactly how to describe the issue I am having. I think I have the issue down to POKE 36869,255 and how the 8k+ RAM expansions reorder the memory map of the computer. I'm not sure how to alter the program to account for this. What I've read online has only confused me more. I'm hoping to understand my error which will hopefully help me to understand how to accomplish what I'm setting out to do. Here is the program that I've written that does the job on the stock machine or 3K expansion:
I have a video of the program running on stock hardware and on 35k to see the difference. I'm using an original VC-20 with PET style keys. The RAM expansion comes from the Penultimate+2 cartridge. I captured the footage by hooking up a 5 pin DIN to composite cable into a composite to HDMI converter and used an HDMI video capture device that plugs into a USB-C port, so it's not terribly great (though incredible that it's possible).
(mod: program source put into code tags)
I am learning how to redefine characters and print them on the screen to make "mostly" full screen images. I can do it just fine for the stock system and with the 3k RAM expansion installed. It would seem that the process is not the same when using an 8k or higher RAM expansion. I'm not entirely sure exactly how to describe the issue I am having. I think I have the issue down to POKE 36869,255 and how the 8k+ RAM expansions reorder the memory map of the computer. I'm not sure how to alter the program to account for this. What I've read online has only confused me more. I'm hoping to understand my error which will hopefully help me to understand how to accomplish what I'm setting out to do. Here is the program that I've written that does the job on the stock machine or 3K expansion:
Code: Select all
10 POKE 36869,255
20 POKE 646,9
30 POKE 36879,136
40 POKE 36878,213
50 POKE 52,28:POKE 56,28:CLR
60 FOR X=0 TO 511
70 POKE 7176+X, PEEK(32768+X)
80 NEXT X
90 FOR X=0 TO 206
100 READ A:POKE 7176+X,A
110 NEXT X
(mod: program source put into code tags)