IRQ Programming

[daybyter]

Hi!

I'm trying to create a simple routine, that is called via NMI, but no luck so far. I followed this posting

viewtopic.php?t=1099#p11462

, but I guess there is something missing.

Thanks in advance for any hint.

Ciao,
Andreas

[PokeMon]

You can not just "CALL" $0281. This will never return to the program as it is not a subroutine. Typically the NMI does a JP (IX) and not a call to that routine. So the stack will be overrun over the time. And IX is changed/toggled wether the display has to be generated or the keyboard has to be read. So you won't have a stable picture.

What you can do is
a) set IX to an own routine
b) do your own stuff
c) setup a toggle bit wether video ($0281) or keyboard ($028f) should be called (jumped !!!)
d) do a jump to $0281 or $028f

At the end you will see, that the video timing is incorrect and picture is not shown good.

So at the end you will have to copy the complete code of $0229 - $028f to RAM, set IX to corresponding address ($0281 doubled in RAM for example) and modify the $0292 routine which starts NMI and restore registers and continue user program. You can put then your code after starting NMI but before restoring the register HL/DE/BC/AF.

[XavSnap]

Have a look to "Monitor" from XavSnap/Nipperroutine:
http://zx81.ordi5.free.fr/xavsnap/download/monitor.zip

Use the « NIPPERROUTINE » to print a Hexadecimal code to the Zxprinter.

Code: Select all

;------- TASM ASM mnemonics. -------
; Compile this file using:
; Set TASMOPTS = -b
; tasm -80 ThisCode.tas MyBinary.BIN
;-----------------------------------
; Zx81 Program name: VB81 XuR [FPH-BAS-MONITOR.P] : SAVE"FPH-BAS-MONITOR" Line 8
; REM   line   name: 2 REM:    77 Bytes@4082-40CE

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

;------------------------------------
;-Basic sub-routine entry.          -
;+----------------------------------+
; Lb4084  ;  <- USR Basic Enty.
;+----------------------------------+

;------- Rom and Ram Symbols -------
RAM_RAMTOP equ $4004
RAM_SPARE2 equ $407B
RAM_STKEND equ $401C
RAM_ERR_SP equ $4002


ORG $4082 ; [@16514/@h4082]
	NOP 
	NOP 
Lb4084: ; <- USR Basic Enty.
	LD HL,(RAM_RAMTOP) ; GET RAM-TOP
	SBC HL,SP 
	LD B,H 
	LD C,L 
	ADD HL,SP 
	DEC HL 
	EX DE,HL 
	LD HL,(RAM_SPARE2) ; GET UNUSED-16
	DEC HL 
	AND A 
	SBC HL,DE 
	JR C, Lb409F ; [$409F:16543]
	JR Z, Lb40C7 ; [$40C7:16583]
	ADD HL,DE 
	EX DE,HL 
	LDDR 
	JR Lb40B3 ; [$40B3:16563]
Lb409F:
	ADD HL,SP 
	PUSH HL 
	LD HL,(RAM_STKEND) ; GET STKEND
	LD DE,$0080 
	ADD HL,DE 
	POP DE 
	SBC HL,DE 
	JR NC, Lb40C7 ; [$40C7:16583]
	LD HL,$0000 
	ADD HL,SP 
	LDIR 
Lb40B3:
	EX DE,HL 
	SBC HL,DE 
	LD D,H 
	LD E,L 
	ADD HL,SP 
	LD SP,HL 
	RR HL,(RAM_E_SP) ; GET ERR-SP
	ADD HL,DE 
	RR (RAM_E_SP),HL ; SET ERR-SP
	LD HL,(RAM_SPARE2) ; GET UNUSED-16
	LD (RAM_RAMTOP),HL ; SET RAM-TOP
Lb40C7:
	LD BC,(RAM_RAMTOP) ; GET RAM-TOP
	RET ; ==========================

Lb40CC:    ; <<< Uncharted Entry ]

	JP $7A3C ; [31292]

.end

Code: Select all

;------- TASM ASM mnemonics. -------
; Compile this file using:
; Set TASMOPTS = -b
; tasm -80 ThisCode.tas MyBinary.BIN
;-----------------------------------
; Zx81 Program name: VB81 XuR [FPH-BAS-MONITOR.P] : SAVE"FPH-BAS-MONITOR" Line 8
; REM   line   name: 4 REM:   299 Bytes@40D5-41FF

#define ORG  .org       ; TASM cross-assembler definitions
#define equ  .equ
;-----------------------------------
;------- Rom and Ram Symbols -------
SLOW equ $0F2B
DISPLAY_5 equ $02B5
DISPLAY_3 equ $0292
LOOP_11 equ $0216
RAM_D_FILE equ $400C
COPY equ $0869
CLS equ $0A2A


ORG $40D5 ; [@16597/@h40D5]
	NOP 
	JR C, Lb40E0 ; [$40E0:16608]
	ADD HL,SP 
	CALL SLOW ; [SLOW]
	LD IX,$7EE7 
Lb40E0:
	CALL $7F27 ; [32551]
	CALL $7FF4 ; [32756]
	RET ; ==========================

Lb40E7:    ; <<< Uncharted Entry ]

	LD A,R 
	LD BC,$1901 
	LD A,$F5 
	CALL DISPLAY_5 ; [DISPLAY-5]
	CALL DISPLAY_3 ; [DISPLAY-3]
	CALL LOOP_11+10 ; []*BIOS ROM*
	LD IX,$7EE7 
	LD H,(IY-81) 
	JP Z,  DISPLAY_3+18 ; []*BIOS ROM*
	LD H,(IY-81) 
	LD HL,(RAM_D_FILE) ; GET D-FILE
	LD BC,$0318 
Lb410A:
	LD A,$10 
	CPIR 
Lb410E:
	JP PO,  DISPLAY_3+18 ; []*BIOS ROM*
	LD A,(HL) 
	CP $76 ; [118]
	JR Z, Lb4123 ; [$4123:16675]
	CP $11 ; [17-")"]
	JR Z, Lb410A ; [$410A:16650]
	SET 7,(HL) 
	LD H,(IY+118) 
	JR Z, Lb4123 ; [$4123:16675]
	RES 7,(HL) 
Lb4123:
	CPI 
	JR Lb410E ; [$410E:16654]
	CALL $7F2E ; [32558]
	CALL $7F2F ; [32559]
	RET ; ==========================

Lb412E:    ; <<< Uncharted Entry ]

	RET ; ==========================

Lb412F:    ; <<< Uncharted Entry ]

	LD HL,(RAM_D_FILE) ; GET D-FILE
	INC HL 
	INC HL 
	LD ($7FFD),HL 
	LD DE,($7FFD) 
	LD HL,($7ED5) 
	CALL $7FB8 ; [32696]
	LD A,$16 
	LD (DE),A 
	INC DE 
	INC DE 
	LD ($7FFD),DE 
	LD A,$08 
	LD ($7FFF),A 
	LD DE,($7FFD) 
	LD HL,($7ED5) 
	LD A,(HL) 
	LD HL,$0000 
	LD L,A 
	CALL $7FE0 ; [32736]
	INC DE 
	LD ($7FFD),DE 
	LD HL,($7ED5) 
	INC HL 
	LD ($7ED5),HL 
	LD BC,($7ED7) 
	INC BC 
	SBC HL,BC 
	RET Z 
	LD A,($7FFF) 
	DEC A 
	LD ($7FFF),A 
	CALL Z,$7F87 ; [32647]
	LD A,($7FFF) 
	CP $08 ; [8]
	JP Z,$7F37 ; [32567]
	JP $7F53 ; [32595]
	LD A,$08 
	LD ($7FFF),A 
	LD HL,($7FFD) 
	LD BC,$0002 
	ADD HL,BC 
	LD ($7FFD),HL 
	LD HL,(RAM_D_FILE) ; GET D-FILE
	LD BC,$0318 
	ADD HL,BC 
	LD BC,($7FFD) 
	SBC HL,BC 
	CALL M,$7FA7 ; [32679]
	RET ; ==========================

Lb41A7:    ; <<< Uncharted Entry ]

	CALL $7FF4 ; [32756]
	LD HL,(RAM_D_FILE) ; GET D-FILE
	INC HL 
	INC HL 
	LD ($7FFD),HL 
	LD A,$08 
	LD ($7FFF),A 
	RET ; ==========================

Lb41B8:    ; <<< Uncharted Entry ]

	LD BC,$D8F0 
	CALL $7FD5 ; [32725]
	LD BC,$FC18 
	CALL $7FD5 ; [32725]
	LD BC,$FF9C 
	CALL $7FD5 ; [32725]
	LD C,$F6 
	CALL $7FD5 ; [32725]
	LD C,$FF 
	CALL $7FD5 ; [32725]
	RET ; ==========================

Lb41D5:    ; <<< Uncharted Entry ]

	LD A,$1B 
Lb41D7:
	INC A 
	ADD HL,BC 
	JR C, Lb41D7 ; [$41D7:16855]
	SBC HL,BC 
	LD (DE),A 
	INC DE 
	RET ; ==========================

Lb41E0:    ; <<< Uncharted Entry ]

	LD A,L 
	CALL $7FE9 ; [32745]
	LD A,L 
	CALL $7FED ; [32749]
	RET ; ==========================

Lb41E9:    ; <<< Uncharted Entry ]

	RRA 
	RRA 
	RRA 
	RRA 
	AND $0F 
	ADD A,$1C 
	LD (DE),A 
	INC DE 
	RET ; ==========================

Lb41F4:    ; <<< Uncharted Entry ]

	LD D,$18 
	CALL COPY+2 ; []*BIOS ROM*
	CALL CLS ; [CLS]
	RET ; ==========================

Lb41FD:    ; <<< Uncharted Entry ]
.end

[daybyter]

Phew,,,,

Thanks a lot for your hints!

I'm new to the zx81 world, so it seems I have a lot to catch up, before I can write more code...