37B77X Datasheet, PDF (57/196 Pages) SMSC Corporation – ENHANCED SUPER I/O CONTROLLER WITH WAKE UP FEATURES

Format A Track
The Format command allows an entire track to
be formatted. After a pulse from the IDX pin is
detected, the FDC starts writing data on the disk
including gaps, address marks, ID fields, and
data fields per the IBM System 34 or 3740
format (MFM or FM respectively). The particular
values that will be written to the gap and data
field are controlled by the values programmed
into N, SC, GPL, and D which are specified by
the host during the command phase. The data
field of the sector is filled with the data byte
specified by D. The ID field for each sector is
supplied by the host; that is, four data bytes per
sector are needed by the FDC for C, H, R, and
N (cylinder, head, sector number and sector size
respectively).
After formatting each sector, the host must send
new values for C, H, R and N to the FDC for the
next sector on the track. The R value (sector
number) is the only value that must be changed
by the host after each sector is formatted. This
allows the disk to be formatted with
nonsequential sector addresses (interleaving).
This incrementing and formatting continues for
the whole track until the FDC encounters a pulse
on the IDX pin again and it terminates the
command.
Table 25 contains typical values for gap fields
which are dependent upon the size of the sector
and the number of sectors on each track. Actual
values can vary due to drive electronics.
FORMAT FIELDS
SYSTEM 34 (DOUBLE DENSITY) FORMAT
DATA
GAP4a SYNC IAM GAP1 SYNC IDAM C H S N C GAP2 SYNC AM
C
80x 12x
50x 12x
Y D E O R 22x 12x
DATA R GAP3 GAP 4b
4E
00
4E 00
L
C
C 4E 00
C
3x FC
3x FE
3x FB
C2
A1
A1 F8
SYSTEM 3740 (SINGLE DENSITY) FORMAT
DATA
GAP4a SYNC IAM GAP1 SYNC IDAM C H S N C GAP2 SYNC AM
C
40x
6x
26x 6x
Y D E O R 11x 6x
DATA R GAP3 GAP 4b
FF
00
FF 00
L
C
C FF 00
C
FC
FE
FB or
F8
PERPENDICULAR FORMAT
DATA
GAP4a SYNC IAM GAP1 SYNC IDAM C H S N C GAP2 SYNC AM
C
80x 12x
50x 12x
Y D E O R 41x 12x
DATA R GAP3 GAP 4b
4E
00
4E 00
L
C
C 4E 00
C
3x FC
3x FE
3x FB
C2
A1
A1 F8
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