dragon64 assembler: string I/O

[Sarah]

I don't think there's really any need to have both a length byte and terminator for your strings, unless you have a special reason for doing that. It's usual just to have a 0 at the end as terminator. The confusion perhaps comes from the fact that the string output ROM routine at $90E5 expects X to point at the byte before the start of a string, hence if you declare a dummy byte before your string that will be fine, but alternatively you can simply subtract 1 from the address instead before executing that call. Since you're writing your own input and output routines anyway, you can choose whatever conventions you prefer.

[heavyfranz]

Here I am.
First, thank you Jeek for welcoming me on the forum and another time thank you all people have replied me

I've spent some time to fix the images but now I think that I could play more better if I post some plain text code...so...after a little work here it is, I've "traduced" Italian constant string to English for clarity.

1) THE PROGRAM THAT WORKS

Code: Select all

*MAIN PROGRAM THAT WORKS
		
		ORG		20001
HEAP	RMB		255
OUTCH	EQU		#%800C ; output char in A reg
					   ; A remain there after
					   ; RTS
INCH	EQU		#$8006 ; store in A the ASCCI
                       ; of the key pressed
					   ; 0 if no key pressed
CR		EQU		$0D
NULL	EQU		$00
TEXT	FCC		8,/STRING=/,0 ; please correct me
		FCB		0             ; here, but I've explained
							  ; what happens if is not
							  ; like here
MAIN	PSHS	U,X,B,A,CC
		LEAX	TEXT,PCR      ; address of 1st char of fixed text
		LDA		#NULL		  ; 0 is the terminator
		PSHS	X,A			  ; pass parameters to subroutine
		BSR		PRINTL        ; go to subroutine "print fixed string"
		LEAS	3,S			  ; I could not waste time
		LEAS	-3,S		  ; and space but for clarity..
							  ; let some space for subroutine results
							  ; 16bit address and 8bit string length
		BSR		GETLNE        ; go to subroutine "input a line from keyboard"
							  ;
		PULS	A,X			  ; extract string length 
		TFR		A,B			  ; that nobody cares at the moment
		LDA		#CR			  ; now we want to print what the user has typed
		PSHS	X,A			  ; pass parameters 
		BSR		PRINTL		  ; print the string
		LEAS	3,S			  ; fix the stack pointer
ENDM	PULS	A,B,X,U,CC,PC ; return to BASIC

*LIBS

******************************************************
*PRINTL - Wants the terminator type and the address of first char only

PRINTL	PSHS	U,X,B,A,CC
		LEAU	7,S
		LDX		3,U			  ; 1st char address
STLOOP	LDA		0,X+
		CMPA	2,U			  ; is what you set for string terminator?
		BEQ		ENDLOP
		JSR		OUTCH
		BRA		STLOOP
ENDLOP	PULS	PC,CC,A,B,X,U

*****************************************************
*GETSCH - Get a single char from keyboard.

GETSCH	PSHS	U,X,B,A,CC
		LEAU	7,S
INPUT	JSR		INCH
		CMPA	#NULL		  ; if 0 key not pressed
		BEQ		INPUT
		STA		2,U           ; store ASCII of key
ENDG	PULS	PC,CC,A,B,X,U

********************************************************
*GETLNE - Get a whole string from the user, CR terminated

GETLNE	PSHS	U,X,B,A,CC
		LEAU	7,S
		LEAX	HEAP,PCR
SCHAR	LEAS	-1,S
		BSR		GETSCH
		PULS	A
		INC     2,U
		STA		,X+
		JSR		OUTCH			; user char
		CMPA	#CR				; is enter?
		BNE		SCHAR
		DECB					; length is without the terminator 
		STB		2,U
		LEAX	HEAP,PCR		; calculate address of 1st char
		STX		3,U				; store it
ENDGTL	PULS	PC,CC,A,B,X,U
		

2) THE PROGRAM THAT NOT WORKS

- constant string are 0 terminated
- user string are terminated with CR
- in the main all the string are redirected to the screen ( one problem at the time...)
- constant string works perfectly
- user string cause what you see in screenshot, garbage + string
- program run and return to basic so I think that there wouldn't be problems in subroutine call

Code: Select all

*MAIN PROGRAM THAT NOT WORKS WITH NEW PRINTL
		
		ORG		20001
HEAP	RMB		255
OUTCH	EQU		#%800C        ; output char in A reg
					          ; A remain there after
					          ; RTS
INCH	EQU		#$8006        ; store in A the ASCCI
                              ; of the key pressed
							  ; 0 if no key pressed
CR		EQU		$0D
NULL	EQU		$00
OUTSER	EQU		#$802D 		  ; from page 336 of "Inside the dragon" seems to behave like OUTCH
							  ; put char in A and it sends out without destroying any register
CH2SER	EQU		$02			  ; select output to serial
CH2SCR	EQU		$01			  ; select output to screen
TEXT	FCC		8,/STRING=/,0 ; please correct me
		FCB		0             ; here, but I've explained
							  ; what happens if is not
							  ; like here (program halts or "memory dump" until a 0 is found
TXT2	FCC		6,/SEND=/,0
		FCB
		
MAIN	PSHS	U,X,B,A,CC
		LEAX	TEXT,PCR      ; address of 1st char of fixed text
		LDA		#NULL		  ; 0 is the terminator
		LDB		#CH2SCR
		PSHS	X,B,		  ; pass parameters to subroutine
		BSR		PRINTL        ; go to subroutine "print fixed string"
							  ; "STRING=" is correctly displayed
		LEAS	4,S			  ; I could not waste time
		LEAS	-3,S		  ; and space but for clarity..
							  ; let some space for subroutine results
							  ; 16bit address and 8bit string length
		BSR		GETLNE        ; go to subroutine "input a line from keyboard"
							  ;
		PULS	A,X			  ; extract string length that nobody cares at the moment
		LDA	 	#CR
		JSR		OUTCH		  ; a newline on the screen
		LDB		#CH2SCR
		LEAX	TXT2,PCR
		PSHS	X,B,A
		BSR		PRINTL		  ; correctly displayed "SEND="
		LEAS	4,S
		LEAX	HEAP,PCR
		LDA		#CR
		LDB		#CH2SCR
		PSHS	X,B,A
		BSR		PRINTL		  ; user string is badly displayed, see screenshot
		LEAS	4,S		      ; but at least the program terminate correctly
ENDM	PULS	A,B,X,U,CC,PC ; return to BASIC

*LIBS

******************************************************
*PRINTL - Wants the terminator type, the address of first char and where to print out

PRINTL	PSHS	U,X,B,A,CC
		LEAU	7,S
		LDB		3,U			  ; what is the output? SCR or 232?
		LDX		4,U			  ; 1st char address
STLOOP	LDA		0,X+
		CMPA	2,U			  ; is what you set for string terminator?
		BEQ		ENDLOP        ; if it's the terminator exit
		CMPB	#CH2SER       ; output to serial?
		BNE		TOSCR		  ; if no output to string
TOSER	JSR		OUTSER
TOSCR	JSR		OUTCH
		BRA		STLOOP
ENDLOP	PULS	PC,CC,A,B,X,U

*****************************************************
*GETSCH - Get a single char from keyboard.

GETSCH	PSHS	U,X,B,A,CC
		LEAU	7,S
INPUT	JSR		INCH
		CMPA	#NULL		  ; if 0 key not pressed
		BEQ		INPUT
		STA		2,U           ; store ASCII of key
ENDG	PULS	PC,CC,A,B,X,U

********************************************************
*GETLNE - Get a whole string from the user, CR terminated

GETLNE	PSHS	U,X,B,A,CC
		LEAU	7,S
		LEAX	HEAP,PCR
SCHAR	LEAS	-1,S
		BSR		GETSCH
		PULS	A
		INC     2,U
		STA		,X+
		JSR		OUTCH			; user char
		CMPA	#CR				; is enter?
		BNE		SCHAR
		DECB					; length is without the terminator 
		STB		2,U
		LEAX	HEAP,PCR		; calculate address of 1st char
		STX		3,U				; store it
ENDGTL	PULS	PC,CC,A,B,X,U
		

From what I've read I've understand that if I declare a string with FCC I have to give address+1 of the string? Is correct? So in memory if i use FCC 4,/AND/,0 constant string are instantiated with LENGHT,MANY CHAR, TERMINATOR ?

I attach edited code scan and screenshot of the nonworking program

PS: gosh...On notepad++ code was beautifully spaced...

work

code_1.png (829 KiB) Viewed 2454 times

not working

code_2.png (806.78 KiB) Viewed 2454 times

screenshot

bad_code.jpg (743.11 KiB) Viewed 2454 times

[Sarah]

I still think your problem is this code trying to output TXT2 using CR as a terminator instead of NULL (0):

LDA #CR
JSR OUTCH ; a newline on the screen
LDB #CH2SCR
LEAX TXT2,PCR
PSHS X,B,A
BSR PRINTL

[heavyfranz]

You're right! I've never seen that error all the time I checked code! A is with the CR for the newline and I forgot to re-set it for TXT2! Now I'll try to patch!


it WORKS!!! Thank you very very very much!