W83977AF Information Storage Devices, Inc, W83977AF Datasheet - Page 51

• Manufacturer Part Number: W83977AF
• Description: W83877TF Plus Kbc, Cir, RTC
• Manufacturer: Information Storage Devices, Inc

Status Register 3 (ST3)
2.2.8 Digital Input Register (DI Register) (Read base address + 7)
The Digital Input Register is an 8-bit read-only register used for diagnostic purposes. In a PC/XT or
AT only Bit 7 is checked by the BIOS. When the register is read, Bit 7 shows the complement of
In the PS/2 mode, the bit definitions are as follows:
DSKCHG (Bit 7):
This bit indicates the complement of the DSKCHG input.
Bit 6-3: These bits are always a logic 1 during a read.
DSKCHG
,
while other bits of the data bus remain in tri-state. Bit definitions are as follows:
7
x
6
x
5
7
7
x
4
6
1
6
x
3
5
1
5
x
x
2
4
1
Reserved for the hard disk controller
During a read of this register, these bits are in tri-state
x
4
1
3
1
3
x
0
2
2
DSKCHG
1
1
0
0
W83977F/ W83977AF
US0 Unit Select 0
TS Two-Side
TO Track 0
WP Write Protected
US1 Unit Select 1
HD Head Address
RY Ready
FT Fault
DRATE0
DRATE1
HIGH DENS
DSKCHG
Publication Release Date: March 1998
-40-
PRELIMINARY
Revision 0.58