w83877atd Winbond Electronics Corp America, w83877atd Datasheet - Page 114

• Manufacturer Part Number: w83877atd
• Description: Winbond I/o
• Manufacturer: Winbond Electronics Corp America

FDD A type 1, 0 (Bit 1, 0):
These two bits select the type of FDD A.
Three mode FDD select (EN3MODE = 1):
8.2.9 Configuration Register 8 (CR8), default = 00H
When the device is in Extended Function mode and EFIR is 08H, the CR8 register can be accessed
through EFDR. The bit definitions are as follows:
Bit 7 - bit 6: Reserved.
DISFDDWR (Bit 5):
This bit enables or disables FDD write data.
Once this bit is set high, the FDC operates normally, but because pin WE is inactive, the FDD will not
write data to diskettes. For example, if a diskette is formatted with DISFDDWR = 1, after the format
command has been executed, messages will be displayed that appear to indicate that the format is
complete. If the diskette is removed from the disk drive and inserted again, however, typing the DIR
command will reveal that the contents of the diskette have not been modified and the diskette was
not actually reformatted.
00
01
10
11
0
1
Selects normal mode. When RWC = 0, the data transfer rate is 250 Kb/s. When
RWC = 1, the data transfer rate is 500 Kb/s.
RWC = 1, selects 1.44 MB high-density FDD.
Don't care RWC
Enables FDD write
Disables FDD write (forces pins WE, WD to stay high)
RWC = 0, selects 1.2 MB high-density FDD.
7
6
,
selects 720 KB double-density FDD.
5
4
3
2
- 110 -
1
0
Floppy Boot Drive 0
Floppy Boot Drive 1
Media ID 0
Media ID 1
SWWP
DISFDDWR
reserved
reserved
Publication Release Date: April 1998
W83877ATF
Version 0.51