pc8477b National Semiconductor Corporation, pc8477b Datasheet - Page 14

• Manufacturer Part Number: pc8477b
• Description: Advanced Floppy Disk Controller
• Manufacturer: National Semiconductor Corporation

3 0 Register Description
D2
D1 – D0
3 10 2 Status Register 1 (ST1)
D7
D6
D5
D4
D3
D2
D1
D0
RESET
COND
DESC
D7
ET
Head Select Indicates the active high status of
the HDSEL pin at the end of the Execution
Phase
Drive Select 1 0 These two binary encoded
bits indicate the logical drive selected at the end
of the Execution Phase
00
01
10
11
End of Track Controller transferred the last
byte of the last sector without the TC pin be-
coming active The last sector is the End of
Track sector number programmed in the Com-
mand Phase
Not Used Always 0
CRC Error If this bit is set and bit 5 of ST2 is
clear then there was a CRC error in the Ad-
dress Field of the correct sector If bit 5 of ST2
is also set then there was a CRC error in the
Data Field
Overrun Controller was not serviced by the mP
soon enough during a data transfer in the Exe-
cution Phase For read operations indicates a
data overrun For write operations indicates a
data underrun
Not Used Always 0
No Data Three possible problems
1 Controller cannot find the sector specified in
2 Controller cannot read any Address Fields
3 Controller cannot find starting sector during
Not Writable Write Protect pin is active when a
Write or Format command is issued
Missing Address Mark If bit 0 of ST2 is clear
then the controller cannot detect any Address
Field Address Mark after two disk revolutions If
bit 0 of ST2 is set then the controller cannot
detect the Data Field Address Mark after finding
the correct Address Field
0
the Command Phase during the execution of
a Read Write Scan or Verify command An
address mark was found however so it is not
a blank disk
without a CRC error during a Read ID com-
mand
execution of Read A Track command
e
e
e
e
D6
Drive 0 selected
Drive 1 selected
Drive 2 selected
Drive 3 selected
0
0
D5
CE
0
OR
D4
0
D3
0
0
(Continued)
ND
D2
0
NW
D1
0
MA
D0
0
14
3 10 3 Status Register 2 (ST2)
D7
D6
D5
D4
D3
D2
D1
D0
3 10 4 Status Register 3 (ST3)
D7
D6
D5
D4
D3
D2
D1 – D0
RESET
RESET
COND
COND
DESC
DESC
D7
D7
Not Used Always 0
Control Mark Controller tried to read a sector
which contained a deleted data address mark
during execution of Read Data or Scan com-
mands Or if a Read Deleted Data command
was executed a regular address mark was de-
tected
CRC Error in Data Field Controller detected a
CRC error in the Data Field Bit 5 of ST1 is also
set
Wrong Track Only set if desired sector is not
found and the track number recorded on any
sector of the current track is different from the
track address specified in the Command Phase
Scan Equal Hit ‘‘Equal’’ condition satisfied dur-
ing any Scan command
Scan Not Satisfied Controller cannot find a
sector on the track which meets the desired
condition during any Scan command
Bad Track Only set if the desired sector is not
found the track number recorded on any sector
on the track is FF (hex) indicating a hard error in
IBM format and is different from the track ad-
dress specified in the Command Phase
Missing Address Mark in Data Field Control-
ler cannot find the Data Field AM during a Read
Scan or Verify command Bit 0 of ST1 is also
set
0
0
Not Used Always 0
Write Protect Indicates active high status of
the WP pin
Not Used Always 1
Track 0 Indicates active high status of the
TRK0 pin
Not Used Always 1
Head Select Indicates the active high status of
the HD bit in the Command Phase
Drive Select 1 0 These two binary encoded
bits indicate the DS1 – DS0 bits in the Command
Phase
0
0
WP
D6
CM
D6
0
0
D5
D5
CD
1
1
0
TK0
D4
WT
D4
0
0
D3
SEH
1
1
D3
0
HDS
D2
0
SNS
D2
0
DS1
D1
0
D1
BT
0
DS0
D0
MD
D0
0
0