pc8477b National Semiconductor Corporation, pc8477b Datasheet - Page 29

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

4 0 Command Set Description
Note 1
Note 2
Note 3 If MT
4 2 22 Version Command
The Version command can be used to determine the floppy
controller being used The Result Phase uniquely identifies
the floppy controller version The PC8477B returns a value
of 90 hex in order to be compatible with the 82077 The
DP8473 and other NEC765 compatible controllers will re-
turn a value of 80 hex (invalid command)
4 2 23 Write Data Command
The Write Data command receives data from the host and
writes logical sectors containing a Normal Data AM to the
selected drive The operation of this command is similar to
the Read Data command except that the data is transferred
from the mP to the controller instead of the other way
around
The controller will simulate the Motor On time before start-
ing the operation If implied seeks are enabled the seek and
sense interrupt functions are then performed The controller
then starts the Data Separator and waits for the Data Sepa-
rator to find the next sector Address Field The controller
compares the Address ID (track head sector bytes per
sector) with the desired ID specified in the Command
Phase If there is no match the controller waits to find the
next sector Address Field This process continues until the
desired sector is found If an error condition occurs the IC
bits in ST0 are set to Abnormal Termination and the con-
troller enters the Result Phase Possible errors are
1 The mP aborted the command by writing to the FIFO If
there is no disk in the drive the controller will hang up
The mP must then take the controller out of this hung
state by writing a byte to the FIFO This will put the con-
troller into the Result Phase
MT
0
0
0
0
1
1
1
1
1
Sectors per Side
Sectors Remaining
e
1 and the SC value is greater than the number of remaining formatted sectors on side 0 verifying will continue on side 1 of the disk
e
e
number of formatted sectors per each side of the disk
number of formatted sectors left which can be read which includes side 1 of the disk if the MT bit is set to 1
EC
0
0
1
1
0
0
1
1
1
TABLE 4-16 Verify Command Result Phase Table
(Continued)
DTL used (should be FF hex)
EOT
DTL used (should be FF hex)
EOT
SC
SC
SC
SC
DTL used (should be FF hex)
EOT
DTL used (should be FF hex)
EOT
SC
SC
SC
EOT
SC
s
s
l
l
s
s
s
l
s
l
s
l
s
EOT
EOT
EOT
(EOT x 2)
(EOT x 2)
SC EOT Value
Sectors per Side
Sectors Remaining
Sectors per Side
Sectors per Side
Sectors per Side
Sectors per Side
Sectors per Side
Sectors per Side
29
AND
AND
AND
OR
2 Two index pulses were detected since the search began
3 The Address Field was found with a CRC error The CE
4 If the controller detects the Write Protect disk interface
If the correct Address Field is found the controller waits for
all (conventional mode) or part (perpendicular mode) of
GAP2 to pass The controller will then write the preamble
field address marks and data bytes to the Data Field The
data bytes are transferred to the controller by the mP
Having finished writing the sector the controller will contin-
ue reading the next logical sector unless one or more of the
following termination conditions occurred
1 The DMA controller asserted TC The IC bits in ST0 are
2 The last sector address (of side 1 if MT was set) was
3 Underrun error The OR bit in ST1 is set The IC bits in
and no valid ID has been found If the track address ID
differs the WT bit or BT bit (if the track address is FF hex)
will be set in ST2 If the head sector or bytes per sector
code did not match the ND bit is set in ST1 If the Ad-
dress Field AM was never found the MA bit is set in ST1
bit is set in ST1
input is asserted bit 1 of ST1 is set
set to Normal Termination
equal to EOT The EOT bit in ST1 is set The IC bits in
ST0 are set to Abnormal Termination This is the expect-
ed condition during Non-DMA transfers
ST0 are set to Abnormal Termination If the mP cannot
service a transfer request in time the last correctly writ-
ten byte will be written to the disk
No Errors
Abnormal Termination
No Errors
Abnormal Termination
No Errors
Abnormal Termination
No Errors
No Errors
Abnormal Termination
Termination Result