PC87332VLJ Datasheet, PDF (57/98 Pages) National Semiconductor (TI) – PC87332VLJ (3.3V/5V) and PC87332VLJ-5 (5V) (SuperI/OTM III Premium Green) Floppy Disk Controller, Dual UARTs, IEEE1284 Parallel Port, and IDE Interfac

4 0 FDC Command Set Description (Continued)
4 3 MNEMONIC DEFINITIONS FOR FDC COMMANDS
Symbol Description
BFR
Buffer enable bit used in the Mode command
Enabled open-collector output buffers
BST
Burst Mode disable control bit used in Mode
command Selects the Non-Burst FIFO mode if
the FIFO is enabled
DC0 – 3
Drive Configuration 0–3 Used to set DC1a
drive to conventional or perpendicular DC2
mode Used in Perpendicular Mode DC3 com-
mand
DENSEL Density Select control bits used in the Mode
command
DIR
Direction control bit used in Relative Seek
command to indicate step in or out
DMA
DMA mode enable bit used in the Specify com-
mand
DR0 – 1
Drive Select 0–1 bits used in most commands
Selects the logical drive
DTL
Data Length parameter used in the Read
Write Scan and Verify commands
EC
Enable Count control bit used in the Verify
command When this bit is 1 the DTL parame-
ter becomes SC (Sector Count)
EIS
Enable Implied Seeks Used in the Configure
command
EOT
End of Track parameter set in the Read Write
Scan and Verify commands
ETR
Extended Track Range used with the Seek
command
FIFO
First-In First-Out buffer Also a control bit used
in the Configure command to enable or disable
the FIFO
FRD
FIFO Read disable control bit used in the
Mode command
FWR
FIFO Write disable control bit used in the
Mode command
GAP
GAP2 control bit used in the Perpendicular
Mode command
HD
Head Select control bit used in most com-
mands Selects Head 0 or 1 of the disk
IAF
Index Address Field control bit used in the
Mode command Enables the ISO Format dur-
ing the Format command
IPS
Implied Seek enable bit used in the Mode
Read Write and Scan commands
LOCK
Lock enable bit in the Lock command Used to
make certain parameters be unaffected by a
software reset
LOW PWR
MFM
MFT
MNT
MT
OW
POLL
PRETRK
PTR
PU
R255
RG
RTN
SC
SK
SRT
ST0 – 3
THRESH
TMR
WG
WLD
Low Power control bits used in the Mode com-
mand
Modified Frequency Modulation control bit
used in the Read Write Format Scan and
Verify commands Selects MFM or FM data
encoding
Motor Off Time programmed in the Specify
command
Motor On Time programmed in the Specify
command
Multi-Track enable bit used in the Read Write
Scan and Verify commands
Overwrite control bit used in the Perpendicular
Mode command
Enable Drive Polling bit used in the Configure
command
Precompensation Track Number used in the
Configure command
Present Track Register Contains the internal
track number for one of the four logical disk
drives
Pump diagnostic enable bit used in the Mode
command
Recalibrate control bit used in Mode com-
mand Sets maximum recalibrate step pulses
to 255
Read Gate diagnostic enable bit used in the
Mode command
Relative Track Number used in the Relative
Seek command
Sector Count control bit used in the Verify
command
Skip control bit used in read and scan opera-
tions
Step Rate Time programmed in the Specify
command Determines the time between step
pulses for seek and recalibrates
Status Register 0 – 3 Contains status ST1 in-
formation about the execution of an ST2 com-
mand Read in the Result Phase of some ST3
commands
FIFO threshold parameter used in the Config-
ure command
Timer control bit used in the Mode command
Affects the timers set in the Specify command
Write Gate control bit used in the Perpendicu-
lar Mode command
Wildcard bit in the Mode command used to en-
able or disable the wildcard byte (FF) during
Scan commands
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