About the Game

Dungeons of Daggorath was a very popular first-person RPG in the early 1980s. It was compatible with the Tandy TRS-80 Color Computer 1/2/3.

It was a very early three-dimensional game that allowed the player to explore a dungeons and battle monsters via a text based interface. That interface is used to move around, fight, pick up or use items, and much more. However, the vast majority of the time, the commands entered revolve around moving and attacking.

For these common actions, the text-based interface can be a bit slow and clunky, so I modified the source code to enable the right joystick (I always wished this was possible as a child). Moving the joystick moves the player around the dungeon, just as would be expected. The button triggers the command ATTACK RIGHT.

Being a first-person game, I could not resist the temptation to insert a few Doom characters in place of some of the originals. The CoCo may not be able to play Doom, but it kinda-sorta can do something like it.

I also gave the player unlimited power and health, which is great for exploring and testing, but that boost can be left out for those that want the challenge.

After assembly, the binary can be burned to a ROM chip mapped into the cartridge port, or should also work with any decent emulator. I assembled the source code with LWASM.

Speaking of source code, the former CEO of DynaMicro, Inc. very graciously released the source code for public distribution, but only in its original form. Since I have modified it, I cannot distribute my work. However, one can still recreate Dungeons of Doom without too much trouble by:

  1. Downloading the original 6809 source code.
  2. Making the modifications I have listed below.
  3. Assembling the code.


Screencaps of modified enemies:


For comparison:


Playing on my CoCo 2:


Modifications to the Original Source Code

  • In CD.ASM:

After line 623, insert the following:

TEMP1   RMB     1                ; NAB
BAGP    RMB     2                ; NAB

Replace line 13 with:

LBNE    PLAY20          ;   yes ; NAB: BNE to LBNE

On line 17, insert the follwing code after the PLAY10 label:

        ; NAB - check for joystick input.
        ; Joystick button.        LDA     65280        ANDA    #1        CMPA    #0        BNE     NOBUTTONPRESS                ; Attack right.        LDU     #PRHAND        JSR     ATTACKRIGHT        JMP     NOMOVE

        JSR     [$A00A]         ; BASIC joystick reading routine.
        LDA     $015B           ; Right joystick y-axis        CMPA    #10        BHI     NOMOVEFORWARD
        ; Move forward        JSR     PMOVEFORWARD        JMP     NOMOVE

        ; Move backward        JSR     PMOVEBACKWARD        JMP     NOMOVE

NOMOVEBACKWARD        LDA     $015A           ; Right joystick x-axis        CMPA    #10        BHI     NOMOVELEFT
        ; Move left        LDB     PDIR        JSR     PMOVELEFT        JMP     NOMOVE

NOMOVELEFT        CMPA    #50        BLO     NOMOVE
        ; Move right        LDB     PDIR        JSR     PMOVERIGHT

NOMOVE        ; NAB - END check for joystick input.

Replace line 47 with:

LBRA    PLAY10         ;loop ; NAB - BRA to LBRA

This is optional, if you want infinte health. After line 40, add:

        CLRA                    ; NAB - IDDQD        CLRB        STD PDAM
  • In ONCE.ASM:

After line 284, add:

        CLR     TEMP1

This is optional, if you want infinite power. After line 288, add:

        LDA     #$7F            ; NAB - Max power.        STA     PPOW

After line 11, add this label:


After line 20, add the label:


After line 29, add the label:


After line 153, add the label:


After line 166, add the label:


On line 16, insert the following after the SOUNDI label:

; NAB - sound back on (reading joystick turns it off)        STA     TEMP1        LDA     $FF23        ORA     #8        STA     $FF23        LDA     TEMP1

Replace line 198 with:

SNRAT1  LBSR     SNOISE          ;get a random noise value ; NAB - L

Replace line 279 with:

SNWSH2  LBSR     SNZNVA          ;get some noise ; NAB - L

Replace line 285 with:

SNWSH1  LBSR     SNENVN          ;decompression subroutine ; NAB - L

On line 309, after the SNOUT label, insert:

 ; NAB - sound back on (reading joystick turns it off)...
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