;; Max 1.5s
.macro time_start
    PHA
    LDA $DC08 ; Bit 0..3: Tenth seconds in BCD-format, others may be 0 or 1
    AND #%00001111
    STA $f1
    PLA
.endmacro

.macro time_stop
    PHA
    LDA $DC08 ; Bit 0..3: Tenth seconds in BCD-format, others may be 0 or 1
    AND #%00001111
    SEC
    SBC $f1
    STA $f1
    PLA
.endmacro