w83977ctf Winbond Electronics Corp America, w83977ctf Datasheet - Page 51

• Manufacturer Part Number: w83977ctf
• 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
ofDSKCHG#
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.
HIGHDENS#(Bit 0):
0
1
500 KB/S or 1 MB/S data rate (high density FDD)
250 KB/S or 300 KB/S data rate
,
while other bits of the data bus remain in tri-state. Bit definitions are as follows:
7
x
6
x
5
x
7
4
1
6
x
3
1
5
x
x
2
1
4
Reserved for the hard disk controller
During a read of this register, these bits are in tri-state
x
1
1
3
-42 -
x
0
2
DSKCHG
1
0
DRATE1
HIGH DENS#
DRATE0
DSKCHG
Publication Release Date: March 1999
W83977EF/ CTF
PRELIMINARY
Revision A1