GM82C803CN Datasheet, PDF (47/84 Pages) List of Unclassifed Manufacturers – 2.88 MB FDC/ Dual UARTs with FIFO/PIO(EPP/ ECP)/ IDE Interface/ S-IR/ PnP

GM82C803CN
Table 4-20. Transfer Capacity
Multitrack
MT
0
0
1
1
0
0
1
1
0
0
1
1
MFM/FM
MF
0
1
0
1
0
1
0
1
0
1
0
1
Bytes/Sector
N
00
01
00
01
01
02
01
02
02
03
02
03
Maximum Transfer Capacity
(Bytes/Sector)
(Number of sectors)
(128) (26) = 3,328
(256) (26) = 6,656
(128) (52) = 6,656
(256) (52) = 13,312
(256) (15) = 3,840
(512) (15) = 7,680
(256) (30) = 7,680
(512) (30) = 15,360
(512) (8) = 4,096
(1024) (8) = 8,192
(512) (16) = 8,192
(1024) (16) = 16,384
Final Sector
Read from
Diskette
26 at side 0
or 26 at side 1
26 at side 1
15 at side 0
or 15 at side 1
15 at side 1
8 at side 0
or 8 at side 1
8 at side 1
The multitrack function (MT) allows the FDC to read data from both sides of the diskette. for a particular cylinder. Data
will be transferred starting at sector 1, side 0 and completing at sector L, side 1 (sector L = last sector on the side). Note, t-
his function pertains to only one cylinder (the same track) on each side of the diskette. When N = 0, then DTL defines the
data length which the FDD must treat as a sector. If DTL is smaller than the actual data length in a sector, the data beyond D-
TL in the sector is not sent to the FIFO, The FDC reads (internally) the complete sector performing the CRC check, and d-
epending upon the manner of command termination, may perform a multi sector read operation. When N is non zero, then
DTL has no meaning and should be set to FF (Hex).
At the completion of the Read Data command, The head is not unloaded until after Head Unload time interval (specified in
the specify command) has elapsed. If the processor issues another command before the head unloads, then the head settling
time may be saved between subsequent reads. This time out is particularly valuable when a diskette is copied from one drive
to another
If the FDC detects the index hole twice without finding the right sector, then the FDC sets the CM (Control Mark) flag in
status Register 2 to a 1, and terminates the Read Data command, after reading all the data in the sector. If SK = 1, the FDC
skips the sector with the Deleted Data Address Mark and reads the next sector. The CRC bits in the deleted data filed a-
re not checked when SK = 1. Table 4-21 shows Sk effect on Read Data command.
Table 4-21. SK Effect on Read Data Command
SK
Data Type
0
Normal
0
Deleted
1
Normal
1
Deleted
Sector Read
Y
Y
Y
N
CM bit (in ST2)
0
1
0
1
Description of results
Normal Termination
No Further Sectors Read
Normal Termination
Sector Skipped