pins in PS/2 and Model 30 modes. The SRA can
be accessed at any time when in PS/2 mode. In
the PC/AT mode the data bus pins D0-D7 are
held in a high impedance state for a read of
address 3F0.
STATUS REGISTER A (SRA)
Address 3F0 READ ONLY
This register is read-only and monitors the state
of the FINTR pin and several disk interface
PS/2 Mode
7
6
5
4
3
2
1
0
INT
nDRV2 STEP nTRK0 HDSEL nINDX nWP
DIR
PENDING
RESET
COND.
0
N/A N/A N/A N/A
0
0
0
BIT 0 DIRECTION
BIT 4 nTRACK 0
Active high status indicating the direction of
head movement. A logic "1" indicates inward
direction; a logic "0" indicates outward direction.
Active low status of the TRK0 disk interface
input.
BIT 5 STEP
BIT 1 nWRITE PROTECT
Active high status of the STEP output disk
interface output pin.
Active low status of the WRITE PROTECT disk
interface input. A logic "0" indicates that the disk
is write protected.
BIT 6 nDRV2
Active low status of the DRV2 disk interface
input pin, indicating that a second drive has
been installed.
BIT 2 nINDEX
Active low status of the INDEX disk interface
input.
BIT 7 INTERRUPT PENDING
Active high bit indicating the state of the Floppy
Disk Interrupt output.
BIT 3 HEAD SELECT
Active high status of the HDSEL disk interface
input. A logic "1" selects side 1 and a logic "0"
selects side 0.
16
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