W83697HF/F
3.2.8
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:
7
6
5
4
3
2
1
0
x x x
x x x
x
Reserved for the hard disk controller
x
During a read of this register, these bits are in tri-state
DSKCHG
In the PS/2 mode, the bit definitions are as follows:
7
6
1
5
4
3
1
2
1
0
1
1
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.
(Bit 0):
HIGH DENS#
0
500 KB/S or 1 MB/S data rate (high density FDD)
1
250 KB/S or 300 KB/S data rate
In the PS/2 Model 30 mode, the bit definitions are as follows:
7
6
5
4
3
2
0
1
0
0
0
DRATE0
DRATE1
NOPREC
DMAEN
DSKCHG
Publication Release Date: Feb. 2002
Revision 0.70
- 44 -
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