ST Memory Map
System Variables
T h e fo llo w in g sy ste m va riab le lo ca tio n s ar e th e o nly o n e s th a t A tari g u ar
a n te es n o t to ch a n g e b etw ee n T O S ve rsio n s. A n y u n d o cu m e n te d v ariab les,
R O M ro u tin es o r ex cep tio n v e c to rs a re alm o st ce rta in to ch a n g e, a n d
sh ou ld n o t b e relied u p o n .
memvalid
1 0 5 6 - 1 0 5 9 ( $ 4 2 0 - $ 4 2 3 )
If th is lo cation co n ta in s th e m ag ic n u m b er $ 75 20 1 9F 3 , an d th e m a g ic n u m
b er in m e m v al2 (1 08 2 , $4 3A ) is also co rre ct, th e n th e co ld sta rt w as s u cce ss
ful, an d th e m e m o ry c on fig u ra tion in m e m cn tlr (b elow ) is co rrec t.
memcntlr
1 0 6 0 - 1 0 6 1 ($ 4 2 4 - $ 4 2 5 )
T h e se co n d n y b b le o f th is w o rd co n ta in s th e co nfig u ra tion va lu e for th e
m em o ry co n tro ller. S om e po ssib le v alu es in clu d e:
V a lu e o f
N y b b le M e m o ry C o n fig u ra tio n
0 128K (o r 25 6K , 2 ban k s)
4 5 1 2K
5 1M b (2 ban k s)
resvalid
1 0 6 2 -1 0 6 5 ($ 4 2 6 - $ 4 2 9 )
If th is lo cation co n tain s th e m ag ic n u m b er $ 31 41 5 92 6, th en o n sys tem re
se t, ex ecu tio n w ill b e d ire cte d th ro u gh re sv ecto r b elo w .
resvector
1 0 6 6 - 1 0 6 9 ( $ 4 2 A - $ 4 2 D )
T h e sy ste m will ju m p th ro u g h th is v ec to r v ery early in th e rese t p ro c es s if
re sv alid is se t to its m ag ic n u m b er.
phystop
1 0 7 0 - 1 0 7 3 ($ 4 2 E - $ 4 3 1 )
T his lo ca tio n p o in t to th e p h ys ical to p of R A M , th e first u n usa ble b yte a t
th e h ig h en d o f th e m e m o ry sp ace (for in sta n ce , $ 8 0 00 0 fo r a 5 1 2K m a
ch in e).
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