GM82C765B Datasheet, PDF (28/36 Pages) Hynix Semiconductor – FLOPPY DISK SUBSYSTEM CONTROLLER

GM82C765B
TABLE 24. SENSE DRIVE STATUS
PHASE
COMMAND
EXECUTION
R/W D7 D6 D5 D4
W
00 00
W
XX XX
ST3
D3 D2 D2 D0
REMARKS
00 0
0 Command Codes
X HS US1 US0
Status information about the FDC
TABLE 25. SEEK
COMMAND
R/W D7 D6 D5 D4
D3 D2 D2 D0
REMARKS
W
0000
W
XXXX
11 1
1 Command Codes
X HS US1 US0
W
NCN
EXECUTION
Head is positioned over proper cylinder
on the diskette.
Table 26 defines, in alphabetical order, the symbols used in Command Tables 11 through 25.
TABLE 26. COMMAND SYMBOL DESCRIPTIONS
SYMBOL
A0
C
D
D7-D0
DTL
EOF
GPL
H
HLT
HS
HUT
MF
MT
NAME
ADDRESS LINE 0
CYLINDER NUMBER
DATA
DATA BUS
DATA LENGTH
END OF TRACK
GAP LENGTH
HEAD ADDRESS
HEAD LOAD TIME
HEAD SELECT
HEAD UNLOAD TIME
FM or MFM
MULTITRACK
DESCRIPTION
A0 Controls selection of Main Status Register (A0 = 0) or Data Register (A0 =1)
C stands for the current/selected cylinder (track) numbers 0 through 255 of the
medium.
D stands for the data pattern which is going to be written into a sector.
8-bit DATA BUS, where D7 stands for a most significant bit, and D) stands for a
least significant bit.
When N is defined as 00, DTL stands for the DATA LENGTH which users are
going to read out or write into the sector.
EOT stands for the final sector number on a cylinder. During read or Write
operations. FDC will stop data transfer after a sector number equal to EOT.
GPL stands for the length of Gap 3. During the FORMAT Command. It
determines the size of Gap 3.
H stands for head number 0 or 1, as specified in the ID field.
HLT stands for the HEAD LOAD TIME in FDD (2 to 254ms in 2ms increments)
HS stands for a selected head number 0 or 1 and controls the polarity of pin 25
(in 40 pin DIP) or pin 28 (in 44 pin PLCC)
HUT stands for the HEAD UNLOAD TIME after a Read or Write operation has
occurred (16 to 240ms in 16ms increments).
If MF is low, FM mode is selected. If it is high, MFM mode is selected.
If MT is high, a MULTITRACK operation is performed.
If MT =1 after finishing Read / Write operation on side 0, FDC will
automatically start searching for sector 1 on side 1
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