Table 41 - Typical Values for Formatting
FORMAT SECTOR SIZE
N
00
00
02
03
04
05
...
SC
12
10
08
04
02
01
GPL1
07
GPL2
09
128
128
512
1024
2048
4096
...
10
19
18
46
C8
C8
30
87
FF
FF
FM
5.25”
Drives
256
01
01
02
03
04
05
...
12
10
09
04
02
01
0A
20
2A
80
C8
C8
0C
32
50
F0
FF
FF
256
512*
1024
2048
4096
...
MFM
128
0
0F
09
05
0F
09
05
07
0F
1B
0E
1B
35
1B
2A
3A
36
54
74
FM
256
1
3.5”
Drives
512
256
512**
1024
2
1
MFM
2
3
GPL1 = suggested GPL values in Read and Write commands to avoid splice point
between data field and ID field of contiguous sections.
GPL2 = suggested GPL value in Format A Track command.
*PC/AT values (typical)
**PS/2 values (typical). Applies with 1.0 MB and 2.0 MB drives.
Note: All values except sector size are in hex.
Control Commands
Control commands differ from the other commands in that no data transfer takes place. Three commands generate
an interrupt when complete: Read ID, Recalibrate, and Seek. The other control commands do not generate an
interrupt.
READ ID
The Read ID command is used to find the present position of the recording heads. The FDC stores the values from
the first ID field it is able to read into its registers. If the FDC does not find an ID address mark on the diskette after
the second occurrence of a pulse on the nINDEX pin, it then sets the IC code in Status Register 0 to “01”
(abnormal termination), sets the MA bit in Status Register 1 to “1”, and terminates the command.
The following commands will generate an interrupt upon completion. They do not return any result bytes. It is highly
recommended that control commands be followed by the Sense Interrupt Status command. Otherwise, valuable
interrupt status information will be lost.
RECALIBRATE
This command causes the read/write head within the FDC to retract to the track 0 position. The FDC clears the
contents of the PCN counter and checks the status of the nTR0 pin from the FDD. As long as the nTR0 pin is low,
the DIR pin remains 0 and step pulses are issued. When the nTR0 pin goes high, the SE bit in Status Register 0 is
set to “1” and the command is terminated. If the nTR0 pin is still low after 79 step pulses have been issued, the
FDC sets the SE and the EC bits of Status Register 0 to “1” and terminates the command. Disks capable of handling
more than 80 tracks per side may require more than one Recalibrate command to return the head back to physical
Track 0. The Recalibrate command does not have a result phase. The Sense Interrupt Status command must be
issued after the Recalibrate command to effectively terminate it and to provide verification of the head position (PCN).
During the command phase of the recalibrate operation, the FDC is in the BUSY state, but during the execution
SMSC DS – FDC37N3869
Page 49
Rev. 10/25/2000
SMSC [ SMSC CORPORATION ]
