ZX81 emulators with built-in assembler... or...?

[TMD2003]

When you start MC (best not to return to BASIC) a simple RND routine can be coded better than use of ROM. I have several.

Bring them on.

Alternatively, I have (on the Spectrum at least) analysed the RND function, isolating all five of the bytes. Apparently the result gets dumped on the calculator stack. One of the bytes makes an almost-consistent random number between 0 and 127 (even if the RND function ensures that there are 65536 values all with an equal probability). If I had a CALL ... to the ROM and then knew where the result was, I could look at it that way.

I may have the ZX81 ROM disassembly somewhere.

And now, I have *another* awful CSSCGC entry to score. It's not Crayon, but it's close.

[dr beep]

When you start MC (best not to return to BASIC) a simple RND routine can be coded better than use of ROM. I have several.

Bring them on.

Alternatively, I have (on the Spectrum at least) analysed the RND function, isolating all five of the bytes. Apparently the result gets dumped on the calculator stack. One of the bytes makes an almost-consistent random number between 0 and 127 (even if the RND function ensures that there are 65536 values all with an equal probability). If I had a CALL ... to the ROM and then knew where the result was, I could look at it that way.

I may have the ZX81 ROM disassembly somewhere.

And now, I have *another* awful CSSCGC entry to score. It's not Crayon, but it's close.

L holds range so this example is a die

Routine does some calculation and seed alters each loop, also timer is used as second parameter.

Code: Select all

rnd        LD   L,6
           LD   A,(frames)
rseed      ADD  A,1
           LD   H,A
           RRCA
           RRCA
           RRCA
           XOR  31
           ADD  A,H
           SBC  A,255
           LD   (rseed+1),A
subl       SUB  L
           JR   NC,subl
        ADC A,L RET
        
  
  

[dr beep]

Another option is to use the ROM as random generator

Read address 0, next 1 etc…. When 8192, go back to 0

[mrtinb]

The template for NO$ZX is tricking me a little, but maybe you should try the online JSZeddy emulator, which has built-in assembler.

So the template I've got so far for NO$ZX is below. There is an error in it, because I cannot get it to autostart. But it's the best I can do for the time being. Good luck.

Code: Select all

.z80
org 16393

;===================
; Header. Don't edit
;===================
db 000h, 002h, 000h

dfileptr: dw dfile

db 0a4h, 040h

vars: dw last

db 000h, 000h

eline: dw afterlast

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nextline: dw dfile
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line1: db 000h, 001h
linelength: dw line2-line1content
line1content:
db 0eah
;===========
; Header end
;===========

;==============
; Program start
;==============
prgstart:
  ld bc,0202h ;print pos 1,1
  call 08f5h  ;set cursor

  ld b,5      ;write 5 chars
again:
  push bc
  pop af
  rst 10h
  djnz again
  ret
;============
; Program end
;============

;=======
; Footer
;=======
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last: db 080h
afterlast:
end

[Spinnetti]

Why constrain yourself with rem statements? I use FASM-ZX which is super basic, no fancy stuff at all, but works great, then just run it with EightyOne. No Rems or basic required.

[mrtinb]

Well NO$ZX has emulator, assembler and debugger in one package, so that's why it was suggested. The built-in directives does not include a Basic REM statement, but uses pure machine code as you suggest. I made the template, as a REM statement was requested

However as we say earlier in the thread, JSZeddy might fit the development cycle even better.

[Spinnetti]

I see. thanks.