w83977tf Winbond Electronics Corp America, w83977tf Datasheet - Page 46

• Manufacturer Part Number: w83977tf
• Description: Winbond I/o
• Manufacturer: Winbond Electronics Corp America

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 DSKCHG
while other bits of the data bus remain in tri-state. Bit definitions are as follows:
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.
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
1
In the PS/2 Model 30 mode, the bit definitions are as follows:
DSKCHG (Bit 7):
500 KB/S or 1 MB/S data rate (high density FDD)
250 KB/S or 300 KB/S data rate
7
x
6
x
5
7
x
4
7
1
6
x
3
6
0
1
5
x
x
2
5
0
1
Reserved for the hard disk controller
During a read of this register, these bits are in tri-state
4
x
1
0
4
1
3
x
0
3
-38-
2
DSKCHG
2
1
1
0
0
DRATE1
HIGH DENS
DRATE0
DSKCHG
DSKCHG
DRATE0
DRATE1
NOPREC
DMAEN
Publication Release Date: April 1998
W83977TF
PRELIMINARY
Revision 0.62
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