Toshiba T1200 - B.4 FUNCTIONS OF THE FDD CONTROLLER; B.4.1 Digital input register (3 F7 H Read)

B. 4 PUHC'l'IORS OF 'l'BB POD COR'fROLLBR
B.4.l Digital input register (3F7H Read)
Bit 7
6
5
4
3 I 2 I 1 1 0
DSCH
EXTB EXTA DSL
Not used
+ DSCH (Disk Change)
When this bit (bit 7) is set to nln, it indicates that
the used disk may have been changed. This bit is
effective only when internal 3.S-inch FDD is used, and
when the external FDD is used, this bit is always set
to "0".
+ EXTB (External FDD B)
When this bit (bit 6) is set to nl", the external FDD
Sel switch is set to Drive B.
+ EXTA (External FDD A)
When this bit (bit S) is set to nln, the external FDD
Sel switch is set to Drive B.
Ext. FDD Sel SW. EFDSL 1
EFDAO Status
1-2
0
1
Ext. FDD Off
Off
1 1 Ext. FDD Drive B
2-3 1
0 Ext. FDD Drive A
B - 7