FDC37C78-HT View Datasheet(PDF) - Microchip Technology
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FDC37C78-HT Datasheet PDF : 82 Pages
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At the completion of the Read Data command, the
head is not unloaded until after the Head Unload
Time Interval (specified in the Specify command)
has elapsed. If the host issues another command
before the head unloads, then the head settling
time may be saved between subsequent reads.
If the FDC detects a pulse on the nINDEX pin
twice without finding the specified sector (meaning
that the diskette's index hole passes through index
detect logic in the drive twice), the FDC sets the IC
code in Status Register 0 to "01" indicating
abnormal termination, sets the ND bit in Status
Register 1 to "1" indicating a sector not found, and
terminates the Read Data Command.
After reading the ID and Data Fields in each
sector, the FDC checks the CRC bytes. If a
CRC error occurs in the ID or data field, the FDC
sets the IC code in Status Register 0 to "01"
indicating abnormal termination, sets the DE bit
flag in Status Register 1 to "1", sets the DD bit in
Status Register 2 to "1" if CRC is incorrect in the
ID field, and terminates the Read Data
Command. Table 22 describes the effect of the
SK bit on the Read Data command execution
and results. Except where noted in Table 22,
the C or R value of the sector address is
automatically incremented (see Table 24).
MT N
Table 21 - Effects of MT and N Bits
MAXIMUM TRANSFER FINAL SECTOR READ
CAPACITY
FROM DISK
0 1 256 x 26 = 6,656
1 1 256 x 52 = 13,312
0 2 512 x 15 = 7,680
1 2 512 x 30 = 15,360
0 3 1024 x 8 = 8,192
1 3 1024 x 16 = 16,384
26 at side 0 or 1
26 at side 1
15 at side 0 or 1
15 at side 1
8 at side 0 or 1
16 at side 1
SK BIT
VALUE
0
0
1
1
Table 22 - Skip Bit vs Read Data Command
DATA ADDRESS
RESULTS
MARK TYPE
SECTOR CM BIT OF DESCRIPTION OF
ENCOUNTERED READ? ST2 SET?
RESULTS
Normal Data
Deleted Data
Normal Data
Deleted Data
Yes
No
Normal
termination.
Yes
Yes
Address not
incremented. Next
sector not
searched for.
Yes
No
Normal
termination.
No
Yes
Normal
termination. Sector
not read
("skipped").
45
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