7Fh Parallel Status/Control Port - Reading 7Fh clears the reset jumpstart logic

7-2 ?
1 Write - SBC200 Memory 0=Active 1=Disabled Read - Parallel Port ISTRB
0 Write - Parallel Port OSTB Read - Parallel Port ORPLY

7Eh Parallel Data Port - Reading 7Eh clears ISTRB and sets IRPLY

7Ch 8251 USART Data Port
7Dh 8251 USART Status/Control Port

7Bh CTC Channel 3
7Ah CTC Channel 2
79h CTC Channel 1
78h CTC Channel 0
7 0=disable 1=Enable Interrups
6 0=Timer 1=Counter
5 0=16 1=256 Prescale in Timer
4 0=Falling 1=Rising Edge
3 0=Auto Trigger 1=Pulse Triggers
2 0=Time Constant Follows
1 1=Reset
0 0=Interrups Vector 1=CCW

67h VF2 FD1795 Data Port
66h VF2 FD1795 Sector Port
65h VF2 FD1795 Track Port
64h VF2 FD1795 Command/Status Port
63h VF2 Control/Status Port (SELECT)

7 Wait State Enable/InUse STB*
6 Double/Single Density 0=SD 1=DD
5 5"/8" Drives 0=8" 1=5.25
4 Side Select 0 or 1
3-0 Drive Select

60h VF2 Reset

01h VDB8024 Data Port

00h VDB8024 Status Port

7-3 ?
2 RDY 0=Busy 1=Ready to accept Data
1 Keyboard Data RDY 1=Valid Input 
0 ?



SBC-200 VDB-8024 vs RS-232

X20 4 to 23 on VDB-8024 open on RS-232
X11 2 to 3 on VDB-8024 1 to 2 on RS-232
X13 open on VDB-8024 2 to 3 on RS-232
VDB EPROM U36 vs RS-232 EPROM in U36