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VT8231
Preliminary Revision 0.8
October 29, 1999
-
50-
Register Descriptions - Super-I/O I/O Ports
7HFKQRORJLHV,QF
:H &RQQHFW
Super-I/O I/O Ports
Floppy Disk Controller Registers
These registers are located at I/O ports which are offsets from
“
FDCBase
”
(index C3h of the Super-I/O configuration
registers). FDCBase is typically set to allow these ports to be
accessed at the standard floppy disk controller address range
of 3F0-3F7h.
Port FDCBase+2
–
FDC Command ................................. RW
7
Motor 3 (unused in VT8231: no MTR3# pin)
6
Motor 2 (unused in VT8231: no MTR2# pin)
5
Motor 1
0
Motor Off
1
Motor On
4
Motor 0
0
Motor Off
1
Motor On
3
DMA and IRQ Channels
0
Disabled
1
Enabled
2
FDC Reset
0
Execute FDC Reset
1
FDC Enabled
1-0
Drive Select
00 Select Drive 0
01 Select Drive 1
1x -reserved-
Port FDCBase+4
–
FDC Main Status ............................... RO
7
Main Request
0
Data register not ready
1
Data register ready
6
Data Input / Output
0
CPU => FDC
1
FDC => CPU
5
Non-DMA Mode
0
FDC in DMA mode
1
FDC not in DMA mode
4
FDC Busy
0
FDC inactive
1
FDC active
3-2
Reserved
........................................ always reads 0
1
Drive 1 Active
0
Drive inactive
1
Drive performing a positioning change
0
Drive 0 Active
0
Drive inactive
1
Drive performing a positioning change
Port FDCBase+4
–
FDC Data Rate Select ...................... WO
Port FDCBase+5
–
FDC Data ......................................... RW
Port FDCBase+7
–
FDC Disk Change Status ................. RO
7
Disk Change
0
Floppy not changed
1
Floppy changed since last instruction
6-3
Undefined
......................................... always read 1
2-1
Data Rate
00 500 Kbit/sec (1.2MB 5
”
or 1.44 MB 3
”
drive)
01 300 Kbit/sec (360KB 5
”
drive)
10 250 Kbit/sec (720KB 3
”
drive)
11 1 Mbit/sec
0
High Density Rate
0
500 Kbit/sec or 1 Mbit/sec selected
1
250 Kbit/set or 300 Kbit/sec selected
Port FDCBase+7
–
FDC Configuration Control ........... WO
7-2
Undefined
......................................... always read 1
1-0
Data Rate
00 500 Kbit/sec (1.2MB 5
”
or 1.44 MB 3
”
drive)
01 300 Kbit/sec (360KB 5
”
drive)
10 250 Kbit/sec (720KB 3
”
drive)
11 1 Mbit/sec