Newb in VDC mmode, needs help blanking screen, then un-blank

stiggity
C-64 User

Posts: 208

Newb in VDC mmode, needs help blanking screen, then un-blank Jun 14, 2020 20:30:59 GMT stiggity likes this

Quote

Post by stiggity on Jun 14, 2020 20:30:59 GMT

Hello:

I was directed to this site from a Facebook user, and have been reading a lot. I'm a beginner writing assembly and get confused quick. The question I have is... Like the c64 your can poke here & there (don't remember the values), and the screen will blank, then by poking a couple other values, you can restore the state the screen was, before it was blanked. I found some save/load source, converted it to my assembler. I got it to compile, but once called the Emulator locks up. How in the world, could I accomplish this, via the c128 in 80 columns?? Please don't Ban me, but I'm going to attempt at posting the code. A personal, Thank You, for any help.

insert code here

*=$1300

JMP vdc_save

jmp vdc_load ;3

vdc_prepare = *

lda #$12

sta vdcstatus

lda hibyte

sta vdc_rw

lda #$13

sta vdcstatus

lda lobyte

sta vdc_rw

lda #$1f

sta vdcstatus

rts

vdc_write = *

notyet bit vdcstatus

bpl notyet

sta vdc_rw ;// writting to VDC

rts

vdc_read = *

notyet1 bit vdcstatus

bpl notyet1

lda vdc_rw ;// reading from VDC

rts

vdc_save = *

ldx #$00

ldy #$10

stx x_w

sty y_w

ldx #$00

ldy #$00

citaj stx x_r

sty y_r

stx lobyte

sty hibyte

jsr vdc_prepare

jsr vdc_read

sta temp

ldx x_w

stx lobyte

ldy y_w

sty hibyte

jsr vdc_prepare

lda temp

jsr vdc_write

inx

stx x_r

stx x_w

ldy y_r

cpx #$00

bne citaj

ldy y_w

iny

sty y_w

tya

and #$0f

tay

sty y_r

cpy #$00

beq done

jmp citaj

done rts

vdc_load = *

ldx #$00

ldy #$00

stx x_w

sty y_w

ldx #$00

ldy #$10

citaj1 stx x_r

sty y_r

stx lobyte

sty hibyte

jsr vdc_prepare

jsr vdc_read

sta temp

ldx x_w

stx lobyte

ldy y_w

sty hibyte

jsr vdc_prepare

lda temp

jsr vdc_write

inx

stx x_r

stx x_w

ldy y_r

cpx #$00

bne citaj1

ldy y_r

iny

sty y_r

tya

and #$0f

tay

sty y_w

cpy #$00

beq done1

ldy y_r

jmp citaj1

done1 rts

vdcstatus .byte 0

hibyte .BYTE 0

LOBYTE .BYTE 0

y_w .byte 0

y_r .byte 0

x_r .byte 0

x_w .byte 0

temp .byte 0

vdc_rw .word 0

;-------------------------------------

Hoping i'm just making a syntax or misunderstanding proper technique.

willymanilly
Global Moderator

Posts: 219

Newb in VDC mmode, needs help blanking screen, then un-blank Jun 15, 2020 0:08:53 GMT

Quote

Post by willymanilly on Jun 15, 2020 0:08:53 GMT

I can see a couple of possible issues with your code.

What assembler are you using? Is it case sensitive? I notice you have declared LOBYTE but reference it as lobyte.
I can't see anywhere in your code where you actually read/write to the VDC registers. I assume you intend vdcstatus and vdc_rw to be references to them. If that is the case then you will need to assign vdcstatus and vdc_rw the actual VDC register locations. Depending on your assembler it should be something like the following.

vdcstatus  = $d600
vdc_rw = $d601

stiggity
C-64 User

Posts: 208

Newb in VDC mmode, needs help blanking screen, then un-blank Jun 15, 2020 1:28:03 GMT via mobile

Quote

Post by stiggity on Jun 15, 2020 1:28:03 GMT

willy:
worked like a charm. not the quickest routine ive ever watched run, but it is doing alot. i was puzzled, but it worked perfect. i use 64tass, and compensate for upper/lowercase in my .bat files iit string. Thanks a million!a

stiggity
C-64 User

Posts: 208

Newb in VDC mmode, needs help blanking screen, then un-blank Jun 15, 2020 4:43:37 GMT

Quote

Post by stiggity on Jun 15, 2020 4:43:37 GMT

Willy... once adding this new routine, into the project... it works. But, when I un-blank the screen, there are artifacts that were definitely not there, before the SAVE??? I wrote/tested in Vice, and just blamed the emulator. Well, since then, I xferred it to my c128, and im experiencing the same artifacts?

Could it be due to me stashing the $FF-long file in $0b00 - $0bff? im out of room in $1300 - $3fff and a lot of my modules reside in $b000 - $bfff. Unfortunately, I don't have room there.. either. I don't believe where it's stored is going to change it's behavior. Any advice? Which!!! is priceless!

bjonte Plus/4 User Posts: 406	Newb in VDC mmode, needs help blanking screen, then un-blank Jun 15, 2020 11:06:55 GMT via Tapatalk Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by bjonte on Jun 15, 2020 11:06:55 GMT Artifacts on which screen?

stiggity C-64 User Posts: 208	Newb in VDC mmode, needs help blanking screen, then un-blank Jun 15, 2020 12:20:22 GMT via mobile Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by stiggity on Jun 15, 2020 12:20:22 GMT on the vdc screen, after the Load.

warty
KIM-1 User

Posts: 29

Newb in VDC mmode, needs help blanking screen, then un-blank Jun 30, 2020 13:50:45 GMT

Quote

Post by warty on Jun 30, 2020 13:50:45 GMT

If you are passing a VDC address to it that is different than the default one, that section of VDC memory could easily be un-initialized. So when you tell the VDC to show it, it would have some junk in it, characters and/or attributes. You'll want to have a routine to clear the attributes and character data.

I have a somewhat generic block fill routine I use to fill VDC screens. At start up, I call this twice, once to write to attribute memory (passing black/non-inverse/lowercase/non-flashing/whatever you want) and once to write spaces to character memory. Hopefully you can make out the core part of this, which is the VDC block fill section.

jsr _Display_VdcGetAddressHi ;// puts HI byte of address associated with c128_zp_screen_id into the A reg.
sta c128_zp_vdc_addr_hi ;// save pointer to screen location (HI)
ldx #00
stx c128_zp_vdc_addr_lo ;// save pointer to screen location (LO) - this routine always copies from start of screen memory
jsr _Display_VdcWriteAddress ;// tell VDC this is the target address

lda c128_zp_other_byte ;// retrieve the fill character
jsr vdc_kernDataWrite ;// vdc_kernDataWrite does the ldx #31

ldx #vdc_reg_v_scroll ;// clear bit 7 of
jsr vdc_kernRegRead ;// register 24 to
and #127 ;// select block fill
jsr vdc_kernRegWrite

; // do the fill/copy operation by repeated writing out the VDC word count to the VDC data register
; // 1 page = 256 bytes. 25x80=2000 bytes = <8 pages. 2000/8=250
; // so 250 is largest block copy we can do and have it end evenly.

ldy #8 ;// clear 8 pages (8*256=2048 bytes to clear)
ldx #vdc_reg_word_count ;// reg 30 is word count
lda #250 ;// 0 words=256 bytes

clear1: jsr vdc_kernRegWrite
dey
bne clear1

rts

oziphantom
C-64 User

Posts: 198

Newb in VDC mmode, needs help blanking screen, then un-blank Jul 1, 2020 7:40:07 GMT

Quote

Post by oziphantom on Jul 1, 2020 7:40:07 GMT

So
Step 1
in


JMP vdc_save
jmp vdc_load ;3 THESE ARE BOTH JUMPS???

Step 2


vdc_prepare = *
lda #$12
sta vdcstatus
lda hibyte
sta vdc_rw ; YOU ARE NOT WAITING FOR THE VDC TO BE READY
lda #$13
sta vdcstatus
lda lobyte
sta vdc_rw
lda #$1f
sta vdcstatus
rts

also in 64Tass you don't need to do
label = *
just do
label
so


vdc_write
notYet bit vdcStatus
bpl notYet

also you can use - for small trivial loops such as


- bit vdcStatus
  bpl -

you can use _ for local labels


func1
    bpl _done
    ..code...
_done
    rts

func2
   bpl _done
   ..code..
_done
   rts

It looks as if you are using this code to copy memory from VDC RAM to another location in VDC RAM, and then you copy it back? This is so you can then blank the visible one? Just set up an clear screen in VDC RAM and adjust the screen pointer to point to the empty one, then move it back to the first one. However if you want to copy and restore, because you are going to modify the contents. You could do an internal DMA copy to move the data.

Commodore 128

Newb in VDC mmode, needs help blanking screen, then un-blank

Post by stiggity on Jun 14, 2020 20:30:59 GMT

Post by willymanilly on Jun 15, 2020 0:08:53 GMT

Post by stiggity on Jun 15, 2020 1:28:03 GMT

Post by stiggity on Jun 15, 2020 4:43:37 GMT

Post by bjonte on Jun 15, 2020 11:06:55 GMT

Post by stiggity on Jun 15, 2020 12:20:22 GMT

Post by warty on Jun 30, 2020 13:50:45 GMT

Post by oziphantom on Jul 1, 2020 7:40:07 GMT

Quick Reply