Spectrum Computing

Posted: **Tue Dec 26, 2017 5:30 pm**

Good to know. I've had a similar experience recently trying to figure out the (low-level) +3DOS stuff. Those multi-byte OUTs/INs, madness.

Posted: **Thu Jan 25, 2018 12:09 pm**

Seven.FFF wrote: ↑Wed Dec 13, 2017 7:39 pm I had been trying to get this one working too. This is the "official" API that passes tokenized basic commands to TR-Dos. I ran into issues with my tokenization - the stuff in my reference REM statements were being tokenised as "C", "O", "D", "E" etc and it was causing confusion with some other problems I was having at the same time. It clearly works in my basic loader though, so I could revisit this later. But I don't really need to.

Hi, I suppose that's because you typed "CODE" in the string as four separate characters instead of the single character 175.

Tokenization of BASIC commands is actually more useful to me since it allows me, with a simple trick, to modify the code of the TR-DOS file management program, so that it can be compatible with the Brazilian clones of the Beta Disk interface, i.e. Arcade AR-20, IDS-91, CBI-95, which point of access for the commands is 15363 instead of 15619. This was pointed to my attention by Flávio Massao Matsumoto, and I have employed it in many of my games.

Code: Select all

LET d = 15363 + 256 * PEEK (15363<>195)

If d = 15619 then it's a standard Beta interface; if d = 15363 the interface is a Brazilian clone. It's then easy to modify the most significant byte of the call to the interface OS in the loading routine to 61 or 60 in order to have the routine work in both cases.

If for instance the call routine is located at 25000:

Code: Select all

25000 034 093 092 LD (CHADD),HL 
25003 205 003 061 CALL 15619  
25006 042 181 097 LD HL,(TEMP)
25009 034 093 092 LD (CHADD),HL	
25012 201 RET
25013 DEFS 2

substituting the byte at 25005 from the BASIC loader before launching the program containing the routine will change 15619 to 15363:

Code: Select all

IF d = 15619 THEN POKE 25005,61
IF d = 15363 THEN POKE 25005,60

Posted: **Thu Jan 25, 2018 2:31 pm**

That’s very useful, thanks Alessandro!

Posted: **Thu Jan 25, 2018 2:47 pm**

You are welcome

Of course HL should point to the BASIC command of the block you wish to load. Another example, related to my post above (loading routine at 25000):

Code: Select all

  
  LD HL, CHADD
  LD (TEMP),HL
  LD HL,BLOCK
  CALL 25000
  RET

BLOCK:
  DEFB 234  ; REM
  DEFM ":"
  DEFB 239  ; LOAD
  DEFB 34   ; "
  DEFM "FILENAME"
  DEFB 34   ; "
  DEFB 175  ; CODE
  DEFB 13   ; [ENTER]

Notice that the CODE function is stored as character 175.

Posted: **Fri Feb 09, 2018 1:05 pm**

Update. This comes from the forthcoming new version of the Al's Double Bill compilation.

Here is the "boot" program for the disk (any BASIC program named "boot" will be executed when RUN is entered at the TR-DOS prompt):

Code: Select all

10 BORDER NOT PI: PAPER NOT PI: INK NOT PI: BRIGHT SGN PI: CLEAR VAL "24499"
20 LET d=VAL "15363"+VAL "256"*(PEEK 15363<>195)
30 RANDOMIZE USR d : REM : LOAD "ADB" CODE
40 RANDOMIZE USR VAL "24500"

Line 20 checks if PEEK 15363 = 195; in this case, d = 15363 and a non-standard Beta Disk interface is connected.

And here is the code for the first MC block loaded from disk. First, it checks the type of Beta Disk interface - standard or not -, then it "recognizes" whether it is running on a 48K or not. Finally, it loads the main selection program accordingly.

The first trick was suggested to me by Einar Saukas, the second by Flávio Matsumoto.

Code: Select all

  ORG 24500
  
  KEY_VAL EQU 24587
  CHADD   EQU 23645
  
  CALL CLEANER
  
  LD HL, ADB_SCR
  LD DE, 16384
  CALL dzx7
  
  LD B,150
  CALL DELAY
  
  LD A,(15363)
  CP 195
  JR NZ, MEMORY     ; if PEEK 15363 <> 195 then a standard Beta Disk is connected

  LD A,60
  LD (KEY_VAL),A      ; ...otherwise it is a clone and the location is modified

MEMORY:

  LD A,(2899)
  CP 165
  JR NZ,ZX128
  
ZX48:

  LD HL,(CHADD)
  LD (TEMP),HL
  LD HL,ADB48
  CALL TRDOS
  JP 32770

ZX128:

  LD HL,(CHADD)
  LD (TEMP),HL
  LD HL,ADB128
  CALL TRDOS
  JP 32770

DELAY:

  HALT
  DJNZ DELAY
  RET

CLEANER:

  LD A,64            ; (64 for BRIGHT 1)
  LD (23693),A       ; PAPER 0, INK 0, BRIGHT 1
  LD (23624),A       ; the last two rows have INK and PAPER set to 0
  CALL 3503          ; CLS
  RET  

TRDOS:

  LD (CHADD),HL
  CALL 15619         ; recalls the TR-DOS loading routine (the last byte here is KEY_VAL)
  LD HL,(TEMP)	     ; reloads CHADD's original value in HL
  LD (CHADD),HL	     ; restores CHADD's original value
  RET

TEMP:	  DEFS 2     ; CHADD's original value is stored here   

ADB48:

	DEFB	234	; REM
	DEFM	":"
	DEFB	239	; LOAD
	DEFB	34	; "
	DEFM	"ADB-48"
	DEFB	34	; "
	DEFB    175     ; CODE
	DEFB	13      ; [ENTER]  

ADB128:

	DEFB	234	; REM
	DEFM	":"
	DEFB	239	; LOAD
	DEFB	34	; "
	DEFM	"ADB-128"
	DEFB	34	; "
	DEFB    175     ; CODE
	DEFB	13      ; [ENTER]

  INCLUDE "dzx7_agileRCS.asm"  ; Einar Saukas's RCS-ZX7 integrated decompressor

ADB_SCR:  INCBIN "ADB-ZX7.bin" ; compressed loading screen

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