Instruction
Set
(3)
-
Instruction Code
Phase R/W
D,
D,
D, D,
D,
D,
D, Do
Remarks
Scan High or Equal
Command
W
MT MF
SK
1
1
1
0
1 Command codes
W
X
X
X
X
X
HD
US,
US,
w+
C Sector ID information prior to command execution.
W+
H
w+
R
W+
N
+
w.
EOT
+
W+
GPL
+
w+
STP
+
Execution
Result R+ STO
-+
Status information after command execution
Data compared between the FDD and main system
R+
ST 1
R+-
ST2
+
R+
C
+
Sector ID information after command execution
N
Recalibrate
Command
W
0 0
0
0
0
1
1 1 Command codes
w
x x
x
x
x
0
us,
us,
Execution
Head retracted to track
0
Sense Interrupt Status
Command
W
0 0
0
0
1
0
0
0
Command codes
Result
R+-
STO
Status information about the FDC at the end of seek operation
R
--
PCN
-+
Specify
Command
W
0 0
0
0 0
0
1 1 Command codes
W
+-
SRT
-+-
HUT
-
w.
HLT ND
Sense Drive Status
Command
W
0
0
0 0 0 1
0 0
Command codes
W
X X
X
X
X
HD US, US,
Result Ri ST3
Status informatin about FDD
Seek
Command
W
0
0 0 0
1
1 1 1
Command codes
W
X
X
X
X X
HD
US,
US,
W+
-
NCN
+
Execution
Invalid
Head is positioned over proper cylinder on diskette
Command
W
t-------
Invalid Codes
-
Result Ri
STO
+
STO=80H
Set Standby
Invalid Command codes (No op
-
FDC goes into standby
state)
Command
W
0
0
1
1
0
1
0
1
Command codes
Execution Enter standby mode
Reset Standby
Command
W
0
0
1 1
0
1
0 0
Command codes
Execution Disable standby mode
Software Reset
Command
W
0 0
1 1
0
1
1
0
Command codes
Execution Same as hardware reset
F-28
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