FDC37C78-HT View Datasheet(PDF) - Microchip Technology
Part Name
Description
Manufacturer
FDC37C78-HT Datasheet PDF : 82 Pages
| |||
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 28 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
49
Share Link: 