Display text followed by the value of a variable

[Tyraniek]

I'd like to do the equivalent of :
:Text(19, 5, "Score :", S
with S = actual score, of course.

I know how to display text :

[Adm.Wiggin]

[Tyraniek]

Perfect !
Exactly what I expected !

thank you.

[Tyraniek]

Oh, and notice that if A=0 (so, if OP1 = 0), it creates a error : "Overflow".
Why ? Did you know it ?

[Adm.Wiggin]

it is because of how dispop1a works... it *supposedly* displays a digits of op1... but i think it only does that if op1 is a decimal... so put ld a,1 in between the 2 functions...

[b__]

I know you can

ld (pencol),hl

and

ld (pencol),a

but can you use bc? Cause i tried to do it, but the coordinates were all screwed up for some reason.

[Job the GameQuitter]

Are you sure you didn't accidently switch horizontal and vertical coordinates?

[John Barrus]

You can only use hl and a to load values into ram addresses...

[Spyderbyte]

But couldn't you load BC into HL?

Spyderbyte

[NETWizz]

I reccomend bcall(_dispHL)

It works like _putS, but displays the value of hl instead and does not need a label or anything.

Now, for loading register hl with register bc, you would do something like this:

ld h,b
ld l,c

Put simply, you need two 8-bit load instructions because ld hl,bc is not a recognized instruction (no opcode in cpu);

Now, if you wish to load ram, load hl or de with the address.

Now, load a or hl depending if you wish to load a byte or a word.

then do something like:

ld (hl),a
ld (de),a
ld (de),hl

Maybe ld (bc),a might work. I do know that ld (hl),bc will not work.

Think of hl as a 16 bit accumulator.

[Justin W.]

[b__]

So then why do the coordinates get all screwed up when I do

ld (pencol),bc

I tried all kinds of different things, but couldn't get it to work right. I tried switching the horizontal and vertical, i tried switching pencol with penrow i tried everything. I finally ended up doing
ld a,b
ld (pencol),a
ld a,c
ld (penrow),a
Oh and i cant use hl because i need to save the address in it. I could push and pop hl, but I think that would be slower.

[Justin W.]

Well my question in turn is how did you load the coordinates into bc?

It should be something to this effect.

ld bc,(column coordinate)*256+(row coordinate)
ld (pencol),bc

So if you wanted to place text at row 10, column 20 you would do this.

ld bc,20*256+10
ld (pencol),bc
ld hl,text
bcall(_vputs)

text:
.db "Hello",0

Now your coodinates will be set. The column coordinate is loaded in front of the row coordinate because pencol comes before penrow in memory. If you need hl then you must push hl before loading the text address into hl and pop it again after the ROM call bcall(_vputs).

[Adm.Wiggin]

very nicely said Justin!

[b__]

This is basically what the actual code is:

ld bc,20*256+60
ld hl,text
call puttext

...

puttext:
ld (pencol),bc
bcall(_vputs)
ret

text:
.db "Text",0

Theoretically there is nothing wrong with the code. What it should do is display text that is halfway off the bottom of the screen, but even if you change the coordinates it still doesn't come out right. But this code works:

ld bc,20*256+60
ld hl,text
call puttext

...

puttext:
ld a,b
ld (pencol),a
ld a,c
ld (penrow),a
bcall(_vputs)
ret

text:
.db "Text",0

Anybody know why? I think that you can't use bc to load into pencol.

[Justin W.]

Well for one thing I don't think it should work at all because you are specifying a row coordinate that is not available to display text. Row coordinates are from 0-57.

[Adm.Wiggin]

yes, it should not work in either senario! but, then again, maybe we r both wrong, and it is colunm 60, row 20!

[Justin W.]

hmm well it appears that my thinking was incorrect. When you load the value into (pencol) it switches the bytes positions, at the ram address. Therefore you must load the row coordinate first then the column.

[b__]

That works! Thanks justin. I have no idea why it works, it just does.