82077AA Datasheet, PDF (23/62 Pages) Intel Corporation – CHMOS SINGLE-CHIP FLOPPY DISK CONTROLLER

82077AA
Symbol Description
DS0 DS1 Disk Drive Select
DS1
DS0
0
0
drive 0
0
1
drive 1
1
0
drive 2
1
1
drive 3
DTL
EC
EFIFO
EIS
EOT
GAP
GPL
H HDS
HLT
HUT
Special sector size By setting N to zero
(00) DTL may be used to control the
number of bytes transferred in disk
read write commands The sector size (N
e _{0) is set to 128 If the actual sector (on}
the diskette) is larger than DTL the re-
mainder of the actual sector is read but is
not passed to the host during read com-
mands during write commands the re-
mainder of the actual sector is written
with all zero bytes The CRC check code
is calculated with the actual sector When
N is not zero DTL has no meaning and
should be set to FF HEX
Enable Count When this bit is ‘‘1’’ the
‘‘DTL’’ parameter of the Verify Command
becomes SC (Number of sectors per
track)
Enable FIFO When this bit is 0 the FIFO
is enabled A ‘‘1’’ puts the 82077AA in
the 8272A compatible mode where the
FIFO is disabled
Enable implied seek When set a seek
operation will be performed before exe-
cuting any read or write command that re-
quires the C parameter in the command
phase A ‘‘0’’ disables the implied seek
End of track The final sector number of
the current track
Alters Gap 2 length when using Perpen-
dicular Mode
Gap length The gap 3 size (Gap 3 is the
space between sectors excluding the
VCO synchronization field)
Head address Selected head 0 or 1
(disk side 0 or 1) as encoded in the sector
ID field
Head load time The time interval that
82077AA waits after loading the head
and before initiating a read or write opera-
tion Refer to the SPECIFY command for
actual delays
Head unload time The time interval from
the end of the execution phase (of a read
or write command) until the head is un-
loaded Refer to the SPECIFY command
for actual delays
Symbol
Lock
MFM
MT
N
Description
Lock defines whether EFIFO FIFOTHR
and PRETRK parameters of the CON-
FIGURE command can be reset to their
default values by a ‘‘Software Reset’’
(Reset made by setting the proper bit in
the DSR or DOR registers)
MFM mode selector A one selects the
double density (MFM) mode
Multi-track selector When set this flag
selects the multi-track operating mode In
this mode the 82077AA treats a com-
plete cylinder under head 0 and 1 as a
single track The 82077AA operates as if
this expanded track started at the first
sector under head 0 and ended at the
last sector under head 1 With this flag
set a multitrack read or write operation
will automatically continue to the first sec-
tor under head 1 when the 82077AA fin-
ishes operating on the last sector under
head 0
Sector size code This specifies the num-
ber of bytes in a sector If this parameter
is ‘‘00’’ then the sector size is 128 bytes
The number of bytes transferred is deter-
mined by the DTL parameter Otherwise
the sector size is (2 raised to the ‘‘N’th’’
power) times 128 All values up to ‘‘07’’
hex are allowable ‘‘07’’h would equal a
sector size of 16k It is the users respon-
sibility to not select combinations that are
not possible with the drive
N
Sector Size
00
128 bytes
01
256 bytes
02
512 bytes
03
1024 bytes
NCN
ND
OW
07
16 Kbytes
New cylinder number The desired cylin-
der number
Non-DMA mode flag When set to 1 indi-
cates that the 82077AA is to operate in
the non-DMA mode In this mode the
host is interrupted for each data transfer
When set to 0 the 82077AA operates in
DMA mode interfacing to a DMA control-
ler by means of the DRQ and DACK
signals
The bits denoted D₀ D₁ D₂ and D₃ of
the PERPENDICULAR MODE command
can only be overwritten when the OW bit
is set to ‘‘1’’
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