PC87307 Datasheet, PDF (87/218 Pages) National Semiconductor (TI) – PC87307/PC97307 Plug and Play Compatible and PC97 Compliant SuperI/O

5.7.1 Abbreviations Used in FDC Commands
BFR Buffer enable bit set in the MODE command. En-
ables open-collector output buffers.
BST Burst mode disable control bit set in MODE com-
mand. Disables burst mode for the FIFO, if the
FIFO is enabled.
DC3-0 Drive Configuration for drives 3-0. Used to config-
ure a logical drive to conventional or perpendicular
mode in the PERPENDICULAR MODE command.
DENSEL
Density Select control bits set in the MODE com-
mand.
DIR Direction control bit used in RELATIVE SEEK com-
mand to indicate step in or out.
DMA DMA mode enable bit set in the SPECIFY com-
mand.
DS1-0 Drive Select for bits 1,0 used in most commands.
Selects the logical drive.
EC Enable Count control bit set in the VERIFY com-
mand. When this bit is 1, SC (Sectors to read
Count) command byte is required.
EIS Enable Implied Seeks. Set in the CONFIGURE
command.
EOT End of Track parameter set in read, write, scan,
and VERIFY commands.
ETR Extended Track Range set in the MODE command.
FIFO First-In First-Out buffer. Also a control bit set in the
CONFIGURE command to enable or disable the
FIFO.
FRD FIFO Read Disable control bit set in the MODE
command
FWR FIFO Write disable control bit set in the MODE
command.
Gap 2 The length of gap 2 in the FORMAT TRACK com-
mand and the portion of it that is rewritten in the
WRITE DATA command depend on the drive
mode, i.e., perpendicular or conventional. Figure
5-20 on page 91 illustrates gap 2 graphically. For
more details, see “Bits 1,0 - Group Drive Mode
Configuration (GDC)” on page 95.
Gap 3 Gap 3 is the space between sectors, excluding the
synchronization field. It is defined in the FORMAT
TRACK command. See Figure 5-20 on page 91.
GDC
Group Drive Configuration for all drives. Configures
all logical drives as conventional or perpendicular.
Used in the PERPENDICULAR MODE command.
Formerly, GAP2 and WG.
HD Head Select control bit used in most commands.
Selects Head 0 or 1 of the disk.
IAF Index Address Field control bit set in the MODE
command. Enables the ISO Format during the
FORMAT command.
IPS Implied Seek enable bit set in the MODE, read,
write, and scan commands.
LOCK Lock enable bit in the LOCK command. Used to
prevent certain parameters from being affected by
a software reset.
LOW PWR
Low Power control bits set in the MODE command.
MFM Modified Frequency Modulation parameter used in
FORMAT TRACK, read, VERIFY and write com-
mands.
MFT Motor Off Time. Now called Delay After Processing
time. This delay is set by the SPECIFY command.
MNT Motor On Time. Now called Delay Before Process-
ing time. This delay is set by the SPECIFY com-
mand.
MSB Most Significant Byte controls which whether the
most or least significant byte is read or written in
the SET TRACK command.
MT Multi-Track enable bit used in read, write, scan and
VERIFY commands.
OW Overwrite control bit set in the PERPENDICULAR
MODE command.
POLL Enable Drive Polling bit set in the CONFIGURE
command.
PRETRK
Precompensation Track Number set in the CON-
FIGURE command
PTR
Present Track number. Contains the internal 8-bit
track number or the least significant byte of the 12-
bit track number of one of the four logical disk
drives. PTR is set in the SET TRACK command.
R255 Recalibration control bit set in MODE command.
Sets maximum number of STEP pulses during
RECALIBRATE command to 255.
RTN Relative Track Number used in the RELATIVE
SEEK command.
SC Sector Count control bit used in the VERIFY com-
mand.
SK Skip control bit set in read and scan and VERIFY
operations.
SRT Step Rate Time set in the SPECIFY command. De-
termines the time between STEP pulses for SEEK
and RECALIBRATE operations.
ST0-3
Result phase Status registers 3-0 that contain sta-
tus information about the execution of a command.
See Sections 5.5.1 through 5.5.4.
THRESH
FIFO threshold parameter set in the CONFIGURE
command
TMR Timer control bit set in the MODE command. Af-
fects the timers set in the SPECIFY command.
WG Formerly, the Write Gate control bit. Now included
in the Group Drive mode Configuration (GDC) bits
in the PERPENDICULAR MODE command.
87
www.national.com