STATUS REGISTER A (SRA)
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.
Address 3F0 READ ONLY
This register is read-only and monitors the state of the
FINTR pin and several disk interface pins,
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" indicating inward direction a logic
"0" outward.
Active low status of the TRK0 disk interface input.
BIT 5 STEP
Active high status of the STEP output disk interface
output pin.
BIT 1 nWRITE PROTECT
Active low status of the WRITE PROTECT disk interface
input. A logic "0" indicating 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
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.
Active high bit indicating the state of the Floppy Disk
Interrupt output.
19
SMSC [ SMSC CORPORATION ]
