TinyMon Version 1.0
Written by JIM BUTTERFIELD
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Jim Butterfield wrote this for one reason. Ha had no ML Monitor back then.
So best solution was obviously DIY strategy back in the days.

You will notice, it is a ML Monitor for hard core users!

To start it, just drag/drop the TinyMon image on the VIC20 emulation screen/
{make sure you have only default RAM set, no expansions}

You can also load it with LOAD"*",8:RUN

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    tinymon

 jim butterfield

b*
   pc  sr ac xr yr sp
.;1b1a 31 40 1b 00 f6

Pure classic by Jim Butterfield, nice!
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And when you hit X and ENTER you get:
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100 print"Sqqr]]] tiny
mon
110 print"q jim butter
field"
120 sys(peek(43)+256*p
eek(44)+078)
ready.

Another classic! That were good old times back then!
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What does it offer?
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6 {Actually 7} commands is what you get! 
Go back in 1982 when you basically had nothing {unless you paid for one} and you typed your 
Machine Code on the paper... in Machine Code! 

	.: 0028 01 04 14 08 14 08 14 08

With the Machine Code Monitors {I am also writing Machine Language Monitors sometimes},
you had a tool in your hands which made your coding life much easier!


Command		Syntax			Doing what?

.R		.R			Will display the CPU registers	 {editable}
.M		.M 0400 0500		Will display bytes in this range {: editable} NOTE: No comma!
.: 		.: 0340 18 60		This is CLC and RTS {It's how you would write a program}
.G		.G 0400			Start the execution from here
.S 		.S"name",08,0400,0500   Saves the range to disk {usually the end address is +1 byte}
.L		.L"name",08		Load a previously saved file to memory
.X		.X			Use to return to BASIC

	   Note: All numbers are hexadecimal!
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Where can you enter your little tiny machine code {assembly} lines?

Tape Buffer area was always a good target are:


. m 0340 03ff {$bf, dec 101 bytes}
	      {Note: You could start already at $33C, dec 828, but i am used to $0340}

.:0340 00 00 00 00 00
.:0345 00 00 00 00 00
.:034a 00 00 00 00 00
.:034f 00 00 00 00 00
.:0354 00 00 00 00 00
.:0359 00 00 00 00 00
.:035e 00 00 00 00 00
.:0363 00 00 00 00 00
.:0368 00 00 00 00 00
.:036d 00 00 00 00 00
.:0372 00 00 00 00 00
.:0377 00 00 00 00 00
.:037c 00 00 00 00 00
....
....
.:03f0 00 00 00 00 00
.:03f5 00 00 00 00 00
.:03fa 00 00 00 00 00
.:03ff 00 04 04 04 04
.
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This is a very huge area to start practice coding in assembly language!

But wait, where are .A and .D commands... Hmmm...

Exactly!

The only way to write a code here is to learn the OP-CODES and use .M command { .: that is}
Basically, without a pen and paper, forget it. 

{well, a text editor will do the job to nowadays ;-)}

Computer Magazines, respectively assembler source code listings, were a great source to get
your hands on tokens and re-use them for own programs.

You can re-use my code {which was used while testing PAL-Assembler for the VIC-20}
And type this in: OP-CODES, {located just on the right from the addresses} and values in TinyMon.

This code is a number one BASIC Helper {Check Pal-Assembler-Test for more details and examples}

$0400 18 	clc
$0401 A2 00	ldx #$00	;lines, 	poke 1026
$0403 a0 00	ldy #$00	;column,	poke 1028
$0405 20 f0 ff	jsr $fff0
$0408 a0 00	ldx #$00	;LOOP start	poke 1033 {NEVER SET X > #$15, dec 21}
$040a a9 20	lda #$20	;SPACE		poke 1035 {ASCII GFX Symbol}
$040c 20 d2 ff	jsr $ffd2
$040f e8	inx
$0410 e0 16	cpx #$16	;END LOOP	poke 1041 {KEEP ALWAYS lower than LOOP START!}
$0412 do f6	bne $040a
$0414 60	rts

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For those who want to try to code like in good old days, i have here {further below}
a listing with some {many} 6502 CPU commands and few other additions. 

This should be enough to bring HELLO WORLD on the screen with TinyMon!

You could proceed like this:

We know that a PRINT {BSOUT} is JSR $ffd2
and ASCII code for Clear Screen is 147, hex #$93
Return is RTS to go back to BASIC, $60 {You always use RTS to go back {return} after the JSR jump call!}

You need to count bytes to have the correct following address {TinyMon can handle only 5 bytes per line}

Decimal	   : 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Hex Numbers: 0 1 2 3 4 5 6 7 8 9  a  b  c  d  e  f

So, it's lda #$93, jsr $ffd2 = .:0340 A9 93 20 d2 ff
			       .:0345 60 00 00 00 00

With this we wrote following:

lda #$93
jsr $ffd2
rts

If you call this from BASIC with SYS 832 it will delete the screen.

6502 is a little endian case, meaning first comes the low byte, then the high byte.
Ergo, out of $ffd2, you'll see or must enter it as follows:

	 $d2 {low byte} and $ff {high byte} = d2 ff in TinyMonitor


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. 01300  69 01    ADC #$01
. 01302  29 01    AND #$01
. 01304  0A       ASL
. 01305  90 F9    BCC $1300
. 01307  B0 F7    BCS $1300
. 01309  F0 F5    BEQ $1300
. 0130B  2C 01 13 BIT $1301
. 0130E  30 F0    BMI $1300
. 01310  D0 EE    BNE $1300
. 01312  10 EC    BPL $1300
. 01314  00       BRK
. 01315  50 E9    BVC $1300
. 01317  70 E7    BVS $1300
. 01319  EA       NOP
. 0131A  EA       NOP
. 0131B  18       CLC
. 0131C  D8       CLD
. 0131D  58       CLI
. 0131E  B8       CLV
. 0131F  C9 0F    CMP #$0F
. 01321  E0 05    CPX #$05
. 01323  C0 08    CPY #$08
. 01325  CE 01 13 DEC $1301
. 01328  CA       DEX
. 01329  88       DEY
. 0132A  4D 06 13 EOR $1306
. 0132D  EE 03 13 INC $1303
. 01330  E8       INX
. 01331  C8       INY
. 01332  4C 1A 13 JMP $131A
. 01335  20 1A 13 JSR $131A
. 01338  A9 FF    LDA #$FF
. 0133A  A2 20    LDX #$20
. 0133C  A0 80    LDY #$80
. 0133E  4E 01 13 LSR $1301
. 01341  EA       NOP
. 01342  09 05    ORA #$05
. 01344  48       PHA
. 01345  08       PHP
. 01346  68       PLA
. 01347  28       PLP
. 01348  2A       ROL
. 01349  6A       ROR
. 0134A  40       RTI
. 0134B  60       RTS
. 0134C  E9 0A    SBC #$0A
. 0134E  38       SEC
. 0134F  F8       SED
. 01350  78       SEI
. 01351  8d 0f 90 sta $900f
. 01354  8e 0f 90 stx $900f
. 01357  8c 0f 90 sty $900f
. 0135A  AA       TAX
. 0135B  A8       TAY
. 0135C  BA       TSX
. 0135D  8A       TXA
. 0135E  9A       TXS
. 0135F  98       TYA

-----------------------------------------------------------
. 01400  bd 00 15 lda $1500,x
. 01403  b9 00 15 lda $1500,y
. 01406  9d 00 15 sta $1500,x
. 01409  99 00 15 sta $1500,y
. 0140c  dd 00 15 cmp $1500,x
. 0140f  d9 00 15 cmp $1500,y
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THIS WILL HELP YOU TO UNDERSTAND HOW IT IS BRANCHED.
IT IS A RELATIVE ADDRESSING. YOU CAN JUM 128 BYTES UP
or 128 DOWN {from the source = branch command}

BRANCHING { LOWER  ADDRESSES }

. 01700  ea       nop
. 01701  ea       nop
. 01702  ea       nop
. 01703  d0 fd    bne $1702
. 01705  d0 fa    bne $1701		Why $fa, dec 250 in $1705?
. 01707  d0 f7    bne $1700		= negative numbers are starting from $80 to $ff
. 01709  ea       nop			= $d0, $fd, $d0, $ea, $ea = 5 = $ff - 5 = $fa		 
. 0170a  ea       nop
. 0170b  ea       nop
. 0170c  f0 fd    beq $170b
. 0170e  f0 fa    beq $170a
. 01710  f0 f7    beq $1709

BRANCHING { HIGHER ADDRESSES }

. 01800  d0 04    bne $1806
. 01802  d0 03    bne $1807		Why $03, dec 4 in $1802?
. 01804  d0 02    bne $1808		= positive numbers are starting from $00 and up to 127
. 01806  ea       nop			= 00 {d0}, 01 {02}, 02 {ea}, 03 {ea} $1807
. 01807  ea       nop
. 01808  ea       nop
. 01809  f0 04    beq $180f
. 0180b  f0 03    beq $1810
. 0180d  f0 03    beq $1812
. 0180f  ea       nop
. 01810  a9 ff    lda #$ff
. 01812  ee 0f 90 inc $900f
. 01815
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Some characters

@abcdefghijklmnopqrtsu
vwyxz   01234567890
!#$%^&*()-=[]

.m 1e00 1e40
.:1e00 00 01 02 03 04
.:1e05 05 06 07 08 09
.:1e0a 0a 0b 0c 0d 0e
.:1e0f 0f 10 11 12 14
.:1e14 13 15 16 17 19
.:1e19 18 1a 20 20 20
.:1e1e 30 31 32 33 34
.:1e23 35 36 37 38 39
.:1e28 30 20 20 20 21
.:1e2d 23 24 25 1e 26
.:1e32 2a 28 29 2d 3d
.:1e37 1b 1d 20 20 20
.:1e3c 20 20 20 20 20
.
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29.05.2026