Changing a double line res. p/m graphics routine into single line res.?

[+Philsan]

I would like to change this routine

http://www.atariarchives.org/c2bag/page103.php

so that players are in single line resolution instead of double line resolution.

Can someone help me?

[Heaven/TQA]

559 is the key...

 

change

 

350 POKE 559,46:POKE 53277,3

 

into

 

350 poke 559,62:poke 53277,3

[+Philsan]

I already know that I have to add 16 to have single line resolution.

The problem is that other things must be changed in the listing, in particular in lines 200-330.

[Rybags]

For single-line, the base has to be on a 2K boundary, not 1K.

 

You'll also need to change offsets and counters of 128 to 256.

 

There's also calculations in there with 512, they need to be changed to 1024.

 

200 A=4*(INT(PEEK(742)/4)-1)

 

That line establishes PMBASE on the 1K boundary below the top of free RAM. So just change the 4s to 8s to align on 2K instead of 1K.

Change the -1 to -2 to reserve 2K.

 

Probably more, but you should be able to work it out.

 

That's a kinda dirty way of doing PMGs in BASIC anyway. It's usually better to just move the screen lower in RAM and use the very top of RAM for PMGs - that way they're well protected from the OS or BASIC just overwriting them.

[+Philsan]

Thanks for your attention, in particular to Rybags.

He changed for me Compute's P/M routine to single line resolution and improved it to protect memory.

Perhaps this routine (it runs in Atari Basic and Turbo-Basic XL) can be useful for newbies.

 

5 REM PMSAMPLE1-SINGLE LINE RESOL.
10 DIM PM1$(256),PM2$(256),PM3$(256)
12 MEMTOP=PEEK(740)
14 POKE 106,MEMTOP-16
16 GRAPHICS 15+16
20 SIZE1=16:SIZE2=8
30 DIM SHIP$(SIZE1),ALIEN$(SIZE2)
40 DIM CLEAR$(256)
50 FOR ROWS=1 TO SIZE1
60 READ DOTS
70 SHIP$(ROWS,ROWS)=CHR$(DOTS)
80 NEXT ROWS
90 DATA 0,0,0,0,0
100 DATA 16,56,56,124,108,68
110 DATA 0,0,0,0,0
120 FOR ROWS=1 TO SIZE2
130 READ DOTS
140 ALIEN$(ROWS,ROWS)=CHR$(DOTS)
145 POKE 53248,X0
150 NEXT ROWS
160 DATA 60,126,219,126,36,36,66,129
170 FOR ROWS=1 TO 256
180 CLEAR$(ROWS,ROWS)=CHR$(0)
190 NEXT ROWS
200 A=MEMTOP-8
210 POKE 54279,A
220 VSA=256*PEEK(135)+PEEK(134)
230 BOA=256*PEEK(141)+PEEK(140)
240 PM=256*A+1024
250 DISP=PM-BOA
260 ADD=2
270 FOR T=1 TO 3
280 PMHIGH=INT(DISP/256)
290 PMLOW=DISP-256*PMHIGH
300 POKE VSA+ADD,PMLOW
310 POKE VSA+ADD+1,PMHIGH
320 DISP=DISP+256:ADD=ADD+8
330 NEXT T
340 PM1$=CLEAR$:PM2$=CLEAR$:PM3$=CLEAR$
350 POKE 559,62:POKE 53277,3
360 COLR1=25:COLR2=11:COLR3=74
370 POKE 704,COLR1:POKE 705,COLR2:POKE 706,COLR3
380 X1=125:X2=75:X3=175
390 POKE 53248,X1:POKE 53249,X2:POKE 53250,X3
400 Y1=95:Y2=65:Y3=65
410 PM1$(Y1)=SHIP$:PM2$(Y2)=ALIEN$:PM3$(Y3)=ALIEN$
420 IF STICK(0)<8 THEN X1=X1+3
430 IF STICK(0)>8 AND STICK(0)<13 THEN X1=X1-3
440 IF STICK(0)=14 THEN Y1=Y1-3
450 IF STICK(0)=13 THEN Y1=Y1+3
460 POKE 53248,X1:PM1$(Y1)=SHIP$
470 IF STICK(1)<8 THEN X2=X2+2
480 IF STICK(1)>8 AND STICK(1)<13 THEN X2=X2-2
490 POKE 53249,X2
500 IF STICK(2)<8 THEN X3=X3+2
510 IF STICK(2)>8 AND STICK(2)<13 THEN X3=X3-2
520 POKE 53250,X3
530 GOTO 420

P107L1SL.zip