lived.ch 14.12.2023 { *update, 05.01.2024 }

* I noticed some logical mistakes while learning the assembly language
* It is corrected now.
* It looks it isn't always turn bit 4 on and it's done.
  It has to be in some cases considered what's already
  activated it needed location and take that into account too.
  In other words, it's what's already running + bit 4
  BUT NOT IN ALL CASES... EASY! hahaha! 

C128_TransferCharacterstoRAM

Location dec 8192, hex $2000
First 128 uppercase and graphics characters
Basic is moved to hex $4000, dec 16384
Activation: lda #$18, sta $02ac (or poke 2604,24)

NOTE: Do not use any of high resolution graphic commands after this!
{ in case you need that, modify the code to transfer to other location, e.g. }
{ dec 12288, $3000, activation with lda #1c, sta $0a2c, or poke 2604,28 }

BANK 14
. 00c00  a9 01    lda #$01
. 00c02  8d 00 ff sta $ff00

BANK 15
. 00c00  a9 01    lda #$00
. 00c02  8d 00 ff sta $ff00

Cursor start location dec 9472, hex $2500
Inverse dec 9984, hex $2700

----------------------------------
TRANSFER CHARACTERS
Instead of @, CURSOR is modified to be an empty box!
btw. @ is still alive! ;-)
----------------------------------
Start with SYS 3130 in BASIC after you have entered the code
in C128 ML Monitor using A command.

A c00 lda #$01 (ENTER) and then so on.
{you can list the entries with D command, e.g. D c00 (ENTER) or D c00 c77 (ENTER) }

SYS 3130

. 00c00  a9 01    lda #$01
. 00c02  8d 00 ff sta $ff00
. 00c05  a2 00    ldx #$00
. 00c07  ea       nop
. 00c08  bd 00 d0 lda $d000,x
. 00c0b  9d 00 20 sta $2000,x
. 00c0e  bd ff d0 lda $d0ff,x
. 00c11  9d ff 20 sta $20ff,x
. 00c14  bd ff d1 lda $d1fe,x
. 00c17  9d ff 21 sta $21fe,x
. 00c1a  bd fd d2 lda $d2fd,x
. 00c1d  9d fd 22 sta $22fd,x
. 00c20  e8       inx
. 00c21  e0 ff    cpx #$ff
. 00c23  d0 e3    bne $0c08
. 00c25  a9 06    lda #$06
. 00c27  8d 20 d0 sta $d020
. 00c2a  a9 07    lda #$07
. 00c2c  85 f1    sta $f1
. 00c2e  a9 00    lda #$00
. 00c30  8d 00 ff sta $ff00
. 00c33  a9 18    lda #$18
. 00c35  8d 2c 0a sta $0a2c
. 00c38  60       rts
. 00c39  ea       nop
. 00c3a  20 6b 0c jsr $0c6b
. 00c3d  20 00 0c jsr $0c00
. 00c40  a9 06    lda #$06
. 00c42  8d 21 d0 sta $d021
. 00c45  ea       nop
. 00c46  a9 ff    lda #$ff
. 00c48  8d 00 25 sta $2500
. 00c4b  a9 81    lda #$81
. 00c4d  8d 01 25 sta $2501
. 00c50  8d 02 25 sta $2502
. 00c53  8d 03 25 sta $2503
. 00c56  8d 04 25 sta $2504
. 00c59  8d 05 25 sta $2505
. 00c5c  8d 06 25 sta $2506
. 00c5f  a9 ff    lda #$ff
. 00c61  8d 07 25 sta $2507
. 00c64  a9 00    lda #$00
. 00c66  aa       tax
. 00c67  9d 00 04 sta $0400,x
. 00c6a  60       rts
. 00c6b  ea       nop
. 00c6c  a9 ff    lda #$ff
. 00c6e  85 d8    sta $d8
. 00c70  a9 3b    lda #$3b
. 00c72  8d 11 d0 sta $d011
. 00c75  a9 1b    lda #$1b
. 00c77  8d 11 d0 sta $d011
. 00c7a  a9 00    lda #$00
. 00c7c  85 d8    sta $d8
. 00c7e  60       rts

Commented version
{ code looks a bit messy, but i wrote it directly }
{ in ML Monitor of C128. It's actually pretty clear, haha... }
{ You can re-order it if you wish to }

. 00c00  a9 01    lda #$01		- switch to bank 14
. 00c02  8d 00 ff sta $ff00		- to access characters in ROM
. 00c05  a2 00    ldx #$00		- reset counter
. 00c07  ea       nop			- NOPs are here to eat memory for free ;-)
. 00c08  bd 00 d0 lda $d000,x		- start loading characters
. 00c0b  9d 00 20 sta $2000,x		- and transfer them to our reserved location 
. 00c0e  bd ff d0 lda $d0ff,x		- $2000 or dec 8192
. 00c11  9d ff 20 sta $20ff,x		
. 00c14  bd ff d1 lda $d1ff,x
. 00c17  9d ff 21 sta $21ff,x
. 00c1a  bd fd d2 lda $d2fd,x
. 00c1d  9d fd 22 sta $22fd,x		- all 128 (0-127) characters, uppercase plus graphic	
. 00c20  e8       inx
. 00c21  e0 ff    cpx #$ff
. 00c23  d0 e3    bne $0c08		- loop until done
. 00c25  a9 06    lda #$06		- screen color
. 00c27  8d 20 d0 sta $d020
. 00c2a  a9 07    lda #$07		- text color
. 00c2c  85 f1    sta $f1
. 00c2e  a9 00    lda #$00
. 00c30  8d 00 ff sta $ff00		- switch back to BANK 15
. 00c33  a9 18    lda #$18		- pointer to our new character location
. 00c35  8d 2c 0a sta $0a2c		- in RAM (where it can be modified)
. 00c38  60       rts			- back to $00c40
. 00c39  ea       nop
. 00c3a  20 6b 0c jsr $0c6b		- jump to subroutine to reserve space
. 00c3d  20 00 0c jsr $0c00		- when reservation is done, jump to transfer chars
. 00c40  a9 06    lda #$06		- screen color	
. 00c42  8d 21 d0 sta $d021
. 00c45  ea       nop
. 00c46  a9 ff    lda #$ff		- transform the CURSOR to a rectangle
. 00c48  8d 00 25 sta $2500		- 8 bytes starting at $2500, or dec 9472
. 00c4b  a9 81    lda #$81
. 00c4d  8d 01 25 sta $2501
. 00c50  8d 02 25 sta $2502
. 00c53  8d 03 25 sta $2503
. 00c56  8d 04 25 sta $2504
. 00c59  8d 05 25 sta $2505
. 00c5c  8d 06 25 sta $2506
. 00c5f  a9 ff    lda #$ff
. 00c61  8d 07 25 sta $2507		- and done.		
. 00c64  a9 00    lda #$00		- show it at location 1024
. 00c66  aa       tax
. 00c67  9d 00 04 sta $0400,x
. 00c6a  60       rts			- back to BASIC
. 00c6b  ea       nop	
. 00c6c  a9 ff    lda #$ff		- disable Basic interrupt
. 00c6e  85 d8    sta $d8		- or we can't switch to graphic mode
. 00c70  a9 3b    lda #$3b		- switch to highres and back
. 00c72  8d 11 d0 sta $d011		- to reserve space. BASIC is now at $4000, not $1c01 as usually 
. 00c75  a9 1b    lda #$1b		- WARNING: do not use bitmaps anymore
. 00c77  8d 11 d0 sta $d011		- meaning highres graphic commands!
. 00c7a  a9 00    lda #$00		- turn interrupt on
. 00c7c  85 d8    sta $d8		- to be able to switch to new character set
. 00c7e  60       rts			- back to $00c3d


 
Hint:
To modify characters as you wish, use EDASS 128 (or other assembler editors for C128) like this:
{ you'll need 4 loops to reach 1024 byte for all 128 characters, 128 chars * 8 bytes = 1024 bytes}
{ or 4x 256 bytes, 4 loops, 1024 bytes transfer }
{ or just 2 loops to modify first 64 uppercase characters }
{ or you can bother with zero page, pointers and page increasing }
{ i preffer this lazy way. it's easy and working fine }


{ first 64 characters, uppercase, 512 bytes }
	
	@abcdefghijklmnopqrstuvwxyz[\]^_  <- you don't see it, but here is SPACE!, $20 or dec 32 ;-)
	!"#$%&'()*+,-./0123456789:;<=>?


charmod = $2000

{ 1st 32 characters }

	ldx# $00
loop1	lda chars1,x
	sta charmod,x
	inx
	cpx #$ff
	bne loop1

{ 2nd 32 characters }

	ldx# $00
loop2	lda chars2,x
	sta charmod+255,x
	inx
	cpx #$ff
	bne loop2

etc. for all characters {graphic and inverse uppercase graphics )

	
;@  { 1st 32 characters }
chars1 	.byte $ff,$81,$81,$81,$81,$81,$81,$ff
;a
	.byte $xx,$xx,$xx,$xx,$xx,$xx,$xx,$xx
;b
	.byte $xx,$xx,$xx,$xx,$xx,$xx,$xx,$xx

;xx { 2nd 32 characters }
chars2 	.byte $xx,$xx,$xx,$xx,$xx,$xx,$xx,$xx
;xx
	.byte $xx,$xx,$xx,$xx,$xx,$xx,$xx,$xx
;xx
	.byte $xx,$xx,$xx,$xx,$xx,$xx,$xx,$xx
etc.

Have fun!