W83877TF Datasheet, PDF (103/154 Pages) Winbond – I/O chip disk drive adapter

W83877TF
FDD A type 1, 0 (Bit 1, 0):
These two bits select the type of FDD A.
00 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.
Three mode FDD select (EN3MODE = 1):
01 RWC = 0, selects 1.2 MB high-density FDD.
10 RWC = 1, selects 1.44 MB high-density FDD.
11 Don't care RWC, selects 720 KB double-density FDD.
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:
765 432 10
Floppy Boot Drive 0
Floppy Boot Drive 1
Media ID 0
Media ID 1
SWWP
DISFDDWR
reserved
reserved
Bit 7 - bit 6: Reserved.
DISFDDWR (Bit 5):
This bit enables or disables FDD write data.
0
Enables FDD write
1
Disables FDD write (forces pins WE, WD to stay high)
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.
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Publication Release Date: March 1998
Version 0.61