Acorn System 6809 card Memory Map
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0000 User RAM
0300 Stack
034C Stack top
034D Monitor variables
03B0 Text input buffer
0400 VDU RAM
0800 CRTC 6845 controller
0900
0980 6522 VIA
     0980 Input/Output Register B
     0981 Input/Output Register A
     0982 Data Direction Register B
     0983 Data Direction Register A
     0984 T1 Low Order Latches/Counter
     0985 T1 High Order Counter
     0986 T1 Low Order Latches
     0987 T1 High Order Latches
     0988 T2 Low Order Latches/Counter
     0989 T2 High Order Counter
     098A Shift Register
     098B Auxilary Control Register
     098C Peripheral Control Register
     098D Interrupt Flag Register
     098E Interrupt Enable Register
     098F Input/Output Register A with no handshake
0A00 FDC (looks like an 8271)
     0A00 Status/Command register
     0A01 Result/Parameter register
     0A02 Reset register
     0A03
     0A04 Data register

0A80

...

F000 Optional additional ROM
F800 Monitor ROM