PC87309 Datasheet, PDF (63/192 Pages) National Semiconductor (TI) – PC87309 SuperI/O Plug and Play Compatible Chip in Compact 100-Pin VLJ Packaging

The Floppy Disk Controller (FDC) (Logical Device 0)
01: Perpendicular. (500 Kbps)
10: Conventional.
11: Perpendicular. (1 or 2 Mbps)
Bits 5-2 -Drive 3-0 Mode Configuration (DC3-0)
If bits 1,0 are both 0, and bit 7 is 1, these bits configure
logical drives 3-0 as conventional or perpendicular. Bits
5-2 (DC3–0) correspond to logical drives 3-0, respec-
tively.
These bits are not affected by a software reset.
0: Conventional drive. (Default)
It is not necessary to issue the FORMAT TRACK
command for conventional drives.
1: Perpendicular drive.
Bit 7 - Overwrite (OW)
This bit enables or disables changes in the mode of the
logical drives by bits 5-2.
0: Changes in mode of logical drives via bits 5-2 are
ignored. (Default)
1: Changes enabled.
Execution Phase
Internal registers are written.
Result Phase
None.
TABLE 3-14. Effect of Drive Mode and Data Rate on FORMAT TRACK and WRITE DATA Commands
Data Rates
250, 300 or 500 Kbps
1 or 2 Mbps
Drive Mode
Conventional
Perpendicular
Conventional
Perpendicular
Length of Gap 2 in FORMAT
TRACK Command
22 bytes
22 bytes
22 bytes
41 bytes
Portion of Gap 2 Rewritten in
WRITE DATA Command
0 bytes
19 bytes
0 bytes
38 bytes
TABLE 3-15. Effect of GDC Bits on FORMAT TRACK and WRITE DATA Commands
GDC Bits
1
0
0
0
0
1
1
0
1
1
Drive Mode
Conventional
Perpendicular (≤500 Kbps)
Conventional
Perpendicular (1 or 2 Mbps)
Length of Gap 2 in
FORMAT TRACK Command
22 bytes
22 bytes
22 bytes
41 bytes
Portion of Gap 2 Rewritten in
WRITE DATA Command
0 bytes
19 bytes
0 bytes
38 bytes
63
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