Dump of ROM content:
And the disassembly, it actually looks like making some sense, though I have not yet tried to analyse it:
ORG 00007H
DIS I ; 0007
DIS TCNTI ; 0008
SEL MB0 ; 0009
SEL RB0 ; 000A
CLR A ; 000B
MOV R2,A ; 000C
MOV R3,A ; 000D
MOV R4,A ; 000E
MOV R6,A ...