6502.org • View topic

View unanswered posts | View active topics

Board index » 6502.org Users Forum » Forth

All times are UTC

U<

Page 1 of 1

[ 3 posts ]

Previous topic | Next topic

Author

Message

powersoft_51

Post subject: U<

Posted: Mon Jul 29, 2024 3:23 pm

Joined: Sat Jun 22, 2024 6:21 am
Posts: 14

I have some trouble with the implemented U< in my figforth for the 6502.
For example :
$7FFF $D800 U< true
$4000 $D800 U< true
$0400 $D800 U< false
$E000 $D800 U< false

The code is :

Code:

1472   0C0E             ;                                       U<
1473   0C0E             ;                                       Unsigned less than
1474   0C0E             ;
1475   0C0E 82 55 BC    L1246     .BYTE $82,"U",$BC
1476   0C11 02 0C                       .WORD L1244    ; link to =
1477   0C13 D6 09       ULESS      .WORD DOCOL
1478   0C15 FA 0B                       .WORD SUB      ; subtract two values
1479   0C17 88 08                       .WORD ZLESS    ; test sign
1480   0C19 0C 08                       .WORD SEMIS

Is there a better code to do this comparision/

Top

GARTHWILSON

Post subject: Re: U<

Posted: Mon Jul 29, 2024 6:08 pm

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8540
Location: Southern California

I have it as a primitive:

Code:

    LDA  3,X
    CMP  1,X
    BNE  1$

    LDA  2,X
    CMP  0,X
1$: BCS  2$
    JMP  POP-TRUE

2$: JMP  POP-FALSE

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Top

JimBoyd

Post subject: Re: U<

Posted: Tue Jul 30, 2024 8:00 pm

Joined: Fri May 05, 2017 9:27 pm
Posts: 895

So do I.

Code:

CODE U< ( N1 N2 -- F )
   2 ,X LDA  0 ,X CMP
   3 ,X LDA  1 ,X SBC
   CS NOT IF  DEY  THEN
   LABEL FLAG.POP
   2 ,X STY  3 ,X STY
   POP JMP  END-CODE

Note: Other primitives in the kernel source use the label FLAG.POP as a branch or jump destination.

Top

Page 1 of 1

[ 3 posts ]

Board index » 6502.org Users Forum » Forth

All times are UTC

Who is online

Users browsing this forum: No registered users and 15 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum