[Coco] Assembly Help

[Chad H]

Ok, I haven't heard from 'theotherbob' yet so I'm throwing this out here .
I know there are people here way smarter than me with this assembly stuff.
I haven't tinkered with it really in 20 years.  Anywhoo.. I found his
article and code archived here.
http://www.oocities.org/theother_bob/PaulDpages/rompak.html  I used this in
conjuction with the Color Basic Unravalled series to hopefully write a sort
of 'bootloader' to join to .BIN file data and write that to a EPROM.  The
idea is to mimic the 'LOADM' routine to transfer EPROM .BIN data to where it
should go and then execute it automatically.  So far I've assembled the code
below in the Rainbow IDE, combined the .BIN data at the end of the code
(FF), and loaded into the M.E.S.S. emulator (CoCo 2) but it just hangs with
a  blank green screen :/

 

I hope I'm not too far off, but wouldn't surprise me.

 

 

                *.BIN single/multisegment bootloader for ROM Pak

                

 

BINDES EQU       BINLOD-EXECJP

                ORG       49152

                

                * VARIABLES

EXECJP  RMB      2                              2 BYTE POINTER FOR EXECUTION
ADDRESS

                

                * LOADEr

LOADER                LDA        #85

BININ    LDX        #BINDES+49152                INIT XFER DATA ADDRESS
OFFSET 

CHKBLK                LDA        ,X+                         GET BLOCK TYPE
BYTE (00 = PREAMBLE, 255=POSTAMBLE)

                BNE        ENDBIN                                IF >0 THEN
MUST BE END OF .BIN DATA (POSTAMBLE)                   

                LDD        ,X++                       GET BLOCK LENGTH(D)

                LDY         ,X++                       GET BLOCK START
ADDRESS(Y)

XFER      LDA        ,X+                         GET SOURCE BYTE(A) FROM X

                STA        ,Y+                          PUT BYTE(A) AT Y

                DECD                                     MOVED BLOCK?

                BNE        XFER                      NO

                JMP       CHKBLK                                CHECK NEXT
BLOCK

ENDBIN                LDD        ,X++                       GET LENGTH
(0000)

                LDY         ,X++                       GET EXECUTION
ADRESS(Y)

                STY         EXECJP

                JMP       [EXECJP]

BINLOD                FCB        255