Screen Store and Recall Basic Routines for VDC in C128
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5 rem vdc screen store/recall demo routines
10 printchr$(147):print"using the two routines given in this sample,"
20 print:print"one can store and recall the vdc screen of c128"
30 print:print:print"for related questions, you can e-mail to ilker ficicilar"
40 print:print"filker@newton.physics.metu.edu.tr"
50 fori=0to14:print:next
60 print"-"tab(32)"press a key"tab(79)"-"chr$(19)tab(79)" "
70 geta$:ifa$=""goto70
80 gosub300:printchr$(147)"press a key to recall the screen back"
90 geta$:ifa$=""goto90
100 gosub200:printchr$(19):fori=0to23:print:next
110 print"issue the 'cont' command to redraw it"
120 end
130 goto100
199 end
200 bank15:rem recalling the vdc 80 screen
210 sysdec("cdcc"),0 ,18:sysdec("cdcc"),0,19
220 sysdec("cdcc"),16,32:sysdec("cdcc"),0,33
230 sysdec("cdcc"),160,24:fori=0to15:sysdec("cdcc"),255,30:next:return
300 bank15:rem storing the vdc 80 screen
310 sysdec("cdcc"),16,18:sysdec("cdcc"),0,19
320 sysdec("cdcc"),0 ,32:sysdec("cdcc"),0,33
330 sysdec("cdcc"),160,24:fori=0to15:sysdec("cdcc"),255,30:next:return
390 :
400 rem related vdc registers
410 :
420 rem 19,18 = destination    (19 = low byte)
430 rem 33,32 = source         (33 = low byte)
440 rem 24    = copy/fill selection
450 rem 30    = number of bytes to be copied
460 :
470 rem vdc memory map
480 :
490 rem $0000-$07ff = screen memory
500 rem $0800-$0fff = attributes memory
510 rem $1000-$1fff = unused (but we used it to store the copy)
520 rem $2000-$3fff = font data (1 char = upper 8 byte of 16 bytes)
530 :
540 rem related kernal calls
550 :
560 rem $cdcc = write to vdc register x the value a
570 rem $cdda = read the vdc register x into a
580 :

Ilker Ficicilar