Missing basic stuff

Trap/Bonzai · Feb 8th 2021

Messing around, trying to learn this beast.

So, if I make a simple assembler program and want to run it on my m65 - in m65 mode. According to the manual, the vic-4 mappings are the same in some areas as the vic-2.

Then, why does setting the screencolor ($d021) f.ex. not work? I know I am missing something about the whole memory layout and knocking stuff. I really don't want to go to c64 mode and open the vic-4 from there. I want to work in native mode.

Sorry about this newbie question

Trap

Shallan · Feb 8th 2021

In order to map in the IO area properly you need to reset the mapping. I do this to enable my VIC4 setup:

Code

//Reset mapping
lda #$00
tax
tay
taz
map
eom
lda #$47 //Enable VIC IV
sta $d02f
lda #$53
sta $d02f

Display More

Trap/Bonzai · Feb 8th 2021

Thanks. Is that also applicable when I run in native ie. Meg65 mode?

Shallan · Feb 8th 2021

Yes. I only run in Mega65 native mode, this is the first thing I do on starting any program

Trap/Bonzai · Feb 8th 2021

Thanks.

One step back here. Can you tell me what is wrong here. I would expect this to constantly flicker the border color, however the program loads, runs, immediately returns to basic. What am I missing?

Code

.cpu _45gs02
.pc = $2001
// Basic start
.word basicend,1
.byte $9e,$38,$32,$32,$34,$00 // SYS 8128
basicend: .word 0
.text "BONZAI"
.pc = $2020
lda #$00 // Reset mapping
tax
tay
taz
map
eom
lda #71 // KEY knock Mega65
sta $d02f
lda #83
sta $d02f
inc $d020
jmp *-3

Display More

Shallan · Feb 8th 2021

Your BASIC upstart needs another line before the SYS, to ensure that the SYS commands runs in the right bank

BANK0

Trap/Bonzai · Feb 8th 2021

Ah ok. Still need to understand why I have to do this. Well, it got me one step further.

Now, what happens is the border goes black, but then it breaks into the monitor. If I stay in the monitor and continue execution in the loop, the border flashes as I expected. How come it breaks into the monitor though?

Code

.cpu _45gs02
.pc = $2001
// Basic start
.word basicend, 2000
.byte $fe,$02,$30,$00 // 2000 BANK 0
.word basicend, 2010
.byte $9e,$38,$32,$32,$34 // 2010 SYS 8128
basicend: .word 0
.text "BONZAI"
.pc = $2020
lda #$00 // Reset mapping
tax
tay
taz
map
eom
lda #71 // KEY knock Mega65
sta $d02f
lda #83
sta $d02f
inc $d020
jmp *-3

Display More

Shallan · Feb 8th 2021

This is due to interrupts. The Mega65 kernel uses raster interrupts unlike the C64 so they start enabled, you need to disable them by either using an SEI, setting $d01a to 0 (after knocking in VIC4) or creating your own replacement raster interrupt.

Trap/Bonzai · Feb 8th 2021

Oh? Thank you, Shallan. So much to learn

Missing basic stuff

Similar Threads

The C256 Foenix Projekt

Mega BASIC - In development

BBC BASIC for the MEGA65?

Xemu Mega65 Emulator update?

BASIC 10 keywords in C65 ROM

Development environment for M65?