Specifications

Signal name
Function / Register
selected
PC-AT
I/O port
address
CS1FX– CS3FX– DA2 DA1 DA0 DIOR– DIOW–
Control Block registers
0 1 0 X X
Data bus
high
impedance
Not used 3F0–3F3
0 1 1 0 X
Data bus
high
impedance
Not used 3F4–3F5
0 1 1 1 0
Alternate
Status
register
Device
Control
register
3F6
0 1 1 1 1
Drive
Address
register
Not used 3F7
4.1 Alternate Status register
CS1FX– = 0 DA2 = 1
CS3FX– = 1 DA1 = 1
DA0 = 0 Mode = Read Only
PC-AT I/O port address: 3F6
H
This register contains the same information as the Status register in the
command block. The only difference is that reading this register does not
imply interrupt acknowledge or reset a pending interrupt. This register
can be read at any time.
Bit 7 6 5 4 3 2 1 0
Name BSY DRDY DWF DSC DRQ CORR IDX ERR
14 ATA Interface Reference Manual, Rev. C