I loaded the following code on the buffalo screen:

*begin
REGBASE EQU $1000
DDRD EQU $09
PORTD EQU $08
SPCR EQU $28
SPSR EQU $29
SPDR EQU $2A

ORG $2000

LDX #REGBASE

LDAA #$21
STAA $40

LDAA #$5C
STAA SPCR,X

LDAA #$3B
STAA DDRD,X

BSET PORTD,X $20

LDAA #$AA
STAA SPDR,X

RTS
*end of code

the ldaa#21 is just to see if the s19 file loads or not. There is an expected change in the memory at $40, and the code loads, but after that nothing happens. the SPCR, SPDR and DDRD remain unchanged. What could be a possible solution.