Sync Magazine v3 n5 page 86 missing

[mrtinb]

I read the article and code several times and could not get how data was returned from ML to B$.

I finally realized that the program needs the variable for return value to be defined as the last variable. The program counts back from E-LINE to the beginning of the variable and fills in the data. Very clever. Then you don’t have to search all variables.

[XavSnap]

Those BASIC listings are bugged... the ASM listings ... too ...

The ASM is designed to be used in a REM (@16514), but Basic listings seem to use this routine after the RAMTOP.

The problem is the "JP NZ,label" /"CALL NZ,label" , how can't be relocate up to the RAMTOP !

The author had to use relative address to use it in annother address.

the correct listing 3, in a rem is:

Code: Select all

# Listing 3.  
     0  REM [HEX:\
21,FA,40,3E,EA,01,FF,FF,\
ED,B1,01,05,00,A7,ED,42,\
3E,76,BE,28,05,09,22,7B,\
40,C9,09,18,E6,2A,7B,40,\
3E,76,BE,CC,85,40,7E,23,\
18,EC,2A,14,40,2B,E5,2B,\
2B,E3,E5,CD,9F,40,E1,06,\
1A,B8,28,0D,77,23,E3,34,\
20,03,23,34,2B,E3,A7,30,\
E9,E3,E1,00,C3,9D,14,2A,\
1C,40,44,4D,21,00,00,39,\
BF,ED,42,44,4D,C9,2A,0C,\
40,44,4D,16,3B,CB,22,2A,\
10,40,0A,BA,28,03,C6,80,\
02,03,BF,ED,42,20,F0,C9,\
2A,04,40,01,88,FF,09,E5,\
E5,D9,C1,D9,21,82,40,D1,\
01,78,00,ED,B0,D9,0B,D3,\
FD,C3,CB,03 ]
1 SAVE "LISTING 3" 
10 LET RS=16514
20 LET RD=RS+42
30 LET FM=RS+79
40 LET IV=RS+94
50 REM COMMANDS ,( USR ) FM IV RS RD , AND GOTO Z,9998,
60 PRINT USR FM
70 RAND USR RS
75 FOR L=1 TO 4
80 LET A$=""
90 RAND USR RD
100 IF L<=3 THEN PRINT A$
105 NEXT L
110 LET Z=VAL A$
120 STOP
9998 LIST 1
9999 RAND USR IV

in ASM CODEs :

Capture.JPG (3.91 KiB) Viewed 6102 times

was 204;133;64

[XavSnap]

Seem OK...

Sync.zip

(63.34 KiB) Downloaded 327 times

Have fun.

[XavSnap]

Commented resources:

Code: Select all

#define ORG  .org       ; TASM cross-assembler definitions
#define equ  .equ
;-----------------------------------

;------- Rom and Ram Symbols -------
EXTERR equ $005B ; Basic Break function ! Ignore line instructions.
CURSEUR equ $8F5 ; Point to PRINT AT DEST.(BC=X,Y)
CHAINE equ $B6B ; PRINT A CHAINE (BC=LEN;DE=TEXT LOC)

; **** SYSTEM VARS ****
RAMTOP equ $4004
D_FILE equ $400C
VARS   equ $4010
E_LINE equ $4014
STKEND equ $401C

; **** ROM ****
NEW    equ $03CB
ROM    equ $149D

ORG 16514
	
; Restore and READ String Routines.  

RESTORE:	; BASIC USR RS 
	LD HL,16634	;  Start @16634 to avoid to point to the header's REM (second REM if exist)
FIND:	LD A,$EA	; CODE "REM" 
	LD BC,$FFFF	; Byte counter, will be decremented.
	CPIR		; DEC BC, CP (HL)<> reg A , INC HL
	LD BC,5		; line header length.
	AND A		; reset F flags (CPIR artefact)
	SBC HL,BC	; REM location - 5
	LD A,118	; N/L code.
	CP (HL)		; If ind. HL value <> A (No N/L before lines arguments)
	JR Z,BELOW	; Go to BELOW label else next...
	ADD HL,BC	; Return to REM location
STASH:	LD (16507),HL	; It's a REM LINE !
	RET 
BELOW:	ADD HL,BC	; It's a REM line, not an ASM OPPCODE. 
	JR FIND		; Scan to the next true REM line.

;  ASM CALL subroutine
READ_CHARACTER: 
	LD HL,(16507)	; REM line location.
	LD A,118	; Test end of line (N/L)
	CP (HL)		; If ind. HL value <> A 
	CALL Z,FIND	; Go to FIND label
	LD A,(HL)	; Copy ind. HL value to A
	INC HL		; INC REM location
	JR STASH	; save the new REM location

;  Basic USR RD value.
READ_STRING:
	LD HL,(E_LINE)	; Read the 'vars' address artefact pointer (LET A$="")
	DEC HL		; Decrement to string length...
	PUSH HL		;  And store it to the top of stack [SP address]
	DEC HL		; Decrement HL'
	DEC HL		; ''''''''''''
	EX (SP),HL	; Exchange contents of HL and top of stack
			; HL=HL-2
LOOP1:	PUSH HL		;  And store it to the top of stack [SP address]
	CALL READ_CHARACTER ; READ a character in the REM line.
	POP HL		; Retrieve HL in stack.
	LD B,26		; Test the next character...
	CP B		; Is it a "," [chr=26] character
COMA_DONE: 
	JR Z,DONE	; If the string is finished, go to DONE label... 
	LD (HL),A	; Copy the character in the vars
	INC HL		; Increment vars value
INC_LEN: 
	EX (SP),HL	; Retrieve the vars len (stored previously E_LINE-1) 
	INC (HL)	; inc its value len A$=Len A$+1
	JR NZ,NO_CARRY	; Test length >FF
	INC HL		; Inc the length high byte
	INC (HL)	; $01;$FF
	DEC HL		; Return to the low byte length byte 
NO_CARRY: 
	EX (SP),HL	; Store the length counter to the previous location

DO_MORE: ; unused label
	AND A		; reset F flags
	JR NC,LOOP1	; !!! Retrieve the 'CP B' status (is it a "," char?)
DONE:	EX (SP),HL	;
	POP HL		;
	NOP
	JP ROM		;Return to the Basic.

;FREE MEMORY Routine.  

FREE_MEM:
	LD HL,(STKEND)	; Get STKEND address
	LD B,H		; STORE HL in BC
	LD C,L 
	LD HL,0		; Reset HL
	ADD HL,SP	; Store SP in HL
	CP A		; ??? A NOT assigned
	SBC HL,BC	; Subtract HL and BC
	LD B,H		; STORE HL in BC
	LD C,L		
	RET		; Return to Basic

; INSTANT REVERSE Routine. 

IV:	LD HL,(D_FILE)	; Get D_FILE address
	LD B,H		; STORE HL in BC
	LD C,L
	LD D,59		; D register = 59
	SLA D		; Shift register left arithmetic
			; D = $76 and clean the F flag
LOOP2:	LD HL,(VARS)	; Get VARS address value
	LD A,(BC)	; Get byte from D_FILE
	CP D		; 
	JR Z,AGAIN	; Value <> $76... next
	ADD A,128	; char+128 
	LD (BC),A	; Refresh D_File
AGAIN:	INC BC		; Inc D_File pointer
	CP A		; $76 ?
	SBC HL,BC	; HL=HL-BC
	JR NZ,LOOP2	; next char.
	RET		; Return to basic

; RELOCATION Routine. 

RELOCATE:
	LD HL,(RAMTOP)	; Get Ramtop
	LD BC,-120	; BC=$FF88
	ADD HL,BC	; RAMTOP + $FF88
	PUSH HL		; store c -2
	PUSH HL		; store stack -1
	EXX		; Exchange register pairs and alt reg pairs
	POP BC		; retrieve BC in stack 
	EXX		; Exchange register pairs and alt reg pairs
	LD HL,16514	; REM location
	POP DE		; retrieve DE in stack 
	LD BC,120	; REM LEN
	LDIR		; Copy REM content HL TO BC
	EXX		; Exchange register pairs and alt reg pairs
	DEC BC		; DEC BC
	OUT (253),A	; ZX81 NMI generator
	JP NEW		; Go to [RAM-CHECK]
.end

Pretty routines !