PC87332VLJ Datasheet, PDF (40/98 Pages) National Semiconductor (TI) – PC87332VLJ (3.3V/5V) and PC87332VLJ-5 (5V) (SuperI/OTM III Premium Green) Floppy Disk Controller, Dual UARTs, IEEE1284 Parallel Port, and IDE Interfac

4 0 FDC Command Set Description (Continued)
4 1 8 Perpendicular Mode Command
The Perpendicular Mode command is designed to support
the unique Format and Write Data requirements of Perpen-
dicular (Vertical) Recording disk drives (4 Mbyte unformat-
ted capacity) The Perpendicular Mode command config-
ures each of the four logical drives as a perpendicular or
conventional disk drive Configuration of the four logical disk
drives is done via the D3–0 bits or with the GAP and WG
control bits This command should be issued during the ini-
tialization of the floppy controller
Command Phase
Perpendicular Recording drives operate in ‘‘Extra High Den-
sity’’ mode at 1 Mbps and 2 Mbps and are downward com-
patible with 1 44 Mbyte and 720 kbyte drives at 500 kbps
(High Density) and 250 kbps (Double Density) respectively
If perpendicular drives are present in the system this com-
mand should be issued during initialization of the floppy con-
troller which configures each drive as perpendicular or con-
ventional Then when a drive is accessed for a Format or
Write Data command the floppy controller adjusts the For-
mat or Write Data parameters based on the data rate select-
ed (see Table 4-6)
0
0
0
1
0
0
1
0
OW 0 DC3 DC2 DC1 DC0 GAP WG
Execution Phase Internal registers are written
Result Phase None
TABLE 4-6 Effect of Drive Mode and Data Rate on Format and Write Commands
Data Rate
250 kbps 300 kbps 500 kbps
1 Mbps 2 Mbps
Drive
Mode
Conventional
Perpendicular
Conventional
Perpendicular
GAP2 Length
Written during
Format
22 Bytes
22 Bytes
22 Bytes
41 Bytes
Portion of GAP2
Re-Written by
Write Data Command
0 Bytes
19 Bytes
0 Bytes
38 Bytes
GAP
0
0
1
1
TABLE 4-7 Effect of GAP and WG on Format and Write Commands
GAP2 Length
Portion of GAP2
Mode
WG
Description
Written during
Re-Written by
Format
Write Data Command
0
Conventional
22 Bytes
0 Bytes
1
Perpendicular
(500 kbps)
22 Bytes
19 Bytes
0
Reserved
(Conventional)
22 Bytes
0 Bytes
1
Perpendicular
(1 Mbps 2 Mbps)
41 Bytes
38 Bytes
40