W83977F-A Datasheet, PDF (44/182 Pages) Winbond – WINBOND I/O

W83977F-A/ W83977G-A/ W83977AF-A/ W83977AG-A
Status Register 3 (ST3)
765
43
210
US0 Unit Select 0
US1 Unit Select 1
HD Head Address
TS Two-Side
TO Track 0
RY Ready
WP Write Protected
FT Fault
5.2.8 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
DSKCHG , while other bits of the data bus remain in tri-state. Bit definitions are as follows:
76 54321 0
xxxxxx x
x ^{Reserved for the hard disk controller}
During a read of this register, these bits are in tri-stat
DSKCHG
In the PS/2 mode, the bit definitions are as follows:
765 43
11 1 1
21
0
HIGH DENS
DRATE0
DRATE1
DSKCHG
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.
DRATE1 DRATE0 (Bit 2, 1):
These two bits select the data rate of the FDC. Refer to the DR register bits 1 and 0 for the settings
corresponding to the individual data rates.
HIGH DENS (Bit 0):
0 500 KB/S or 1 MB/S data rate (high density FDD)
1 250 KB/S or 300 KB/S data rate
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