FDC37M81 SMSC [SMSC Corporation], FDC37M81 Datasheet - Page 59

• Manufacturer Part Number: FDC37M81
• Description: PC98/99 Compliant Enhanced Super I/O Controller with Keyboard/Mouse Wake-Up
• Manufacturer: SMSC [SMSC Corporation]

Format A Track
The Format command allows an entire track to
be formatted. After a pulse from the nINDEX
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).
GAP4a
GAP4a
GAP4a
80x
40x
80x
4E
FF
4E
SYNC
SYNC
SYNC
12x
12x
00
00
00
6x
C2
C2
3x
3x
IAM
IAM
IAM
FC
FC
FC
GAP1
GAP1
GAP1
50x
26x
50x
4E
FF
4E
SYSTEM 3740 (SINGLE DENSITY) FORMAT
SYSTEM 34 (DOUBLE DENSITY) FORMAT
SYNC
SYNC
SYNC
12x
12x
00
00
00
6x
A1
A1
3x
PERPENDICULAR FORMAT
3x
IDAM
IDAM
IDAM
FE
FE
FE
FORMAT FIELDS
C
Y
C
Y
C
Y
L
L
L
H
D
H
D
H
D
C
C
C
S
E
S
E
S
E
59
N
O
N
O
N
O
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
nonsequential sector addresses (interleaving).
This incrementing and formatting continues for
the whole track until the FDC encounters a pulse
on the nINDEX 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.
C
R
C
C
R
C
C
R
C
GAP2
GAP2
GAP2
22x
11x
41x
4E
FF
4E
the
SYNC
SYNC
SYNC
12x
12x
00
00
00
6x
disk
A1
A1
3x
3x
DATA
DATA
DATA
FB or
AM
AM
AM
F8
FB
FB
F8
F8
to
DATA
DATA
DATA
be
C
R
C
C
R
C
C
R
C
formatted
GAP3 GAP 4b
GAP3 GAP 4b
GAP3 GAP 4b
with