PC8477BV-1 National Semiconductor, PC8477BV-1 Datasheet - Page 23

• Manufacturer Part Number: PC8477BV-1
• Description: IC ADVANCED FLOPPY CTRLR 68PLCC
• Manufacturer: National Semiconductor
• Series: SuperFDC™r

Specifications of PC8477BV-1

• Controller Type: Floppy Disk Controller
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 68-LCC (J-Lead)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Supply: -
• Interface: -
• Other names: *PC8477BV-1

4 0 Command Set Description
If IDENT is low the DENSEL pin is active low for the
500 kb s or 1 Mb s data rates In addition to these modes
the DENSEL output can be set to always low or always high
as shown in Table 4-2 This will allow the user more flexibili-
ty with new drive types
Note The DENSEL output values shown below are with the INVERT pin
BFR CMOS Disk Interface Buffer Enable
WLD Scan Wild Card
Head Settle Time allowed for read write head to settle af-
ter a seek during an Implied Seek operation
Note N
RG Read Gate Diagnostic
PU PUMP Pulse Output Diagnostic
1
1
1
0
0
0
0
e
e
e
e
e
e
e
Bit 1
Data Rate
250 kb s
300 kb s
500 kb s
1 Mb s
tied low If the INVERT pin is tied high the outputs shown below have
the opposite polarity
Data Rate
250 kb s
300 kb s
500 kb s
1 Mb s
0
0
1
1
e
Drive output signals configured as standard 4 mA
push-pull outputs (actually 48 mA sink 4 mA
source) (default)
Drive output signals configured as 48 mA open-
drain outputs
An FF (hex) from either the P or the disk during a
Scan command is interpreted as a wildcard charac-
ter that will always match true (default)
The Scan commands do not recognize FF (hex) as
a wildcard character
Enable DSKCHG disk interface input for normal op-
eration (default)
Enable DSKCHG to act as an external Read Gate
input signal to the Data Separator This is intended
as a test mode to aid in evaluation of the Data Sep-
arator
Enable MFM output pin for normal operation (de-
fault)
8 (default)
TABLE 4-3 DENSEL Default Encoding
TABLE 4-2 DENSEL Decoding
Bit 0
0
1
0
1
HST
IDENT
e
N x 8
N x 6 67
N x 4
N x 2
Head Settle Time
high
high
low
low
HST
DENSEL (default)
e
DENSEL Pin Definition
low
high
undefined
DEFAULT
1
IDENT
0–120 ms
0–100 ms
0–60 ms
0–30 ms
Range
high
high
low
low
(Continued)
e
0
23
4 2 7 NSC Command
The NSC command can be used to distinguish between the
PC8477B version and the Intel 82077AA The result Phase
byte uniquely identifies the floppy controller as a PC8477B
which returns a value of 73 hex The 82077AA and DP8473
return a value 80h signifying an invalid command The lower
four bits of this result byte are subject to change by NSC
and will reflect the particular version of the PC8477B part
Note The PC8477A will return a value of 72h in the result phase of the
4 2 8 Perpendicular Mode Command
The Perpendicular Mode command is designed to support
the unique Format and Write Data requirements of Perpen-
dicular (Vertical) Recording disk drives (4 Mbytes unformat-
ted capacity) The Perpendicular Mode command will con-
figure each of the four logical drives as a perpendicular or
conventional disk drive Configuration of the four logical disk
drives is done via the D3– D0 bits or with the GAP and WG
control bits This command should be issued during the ini-
tialization of the floppy controller
Perpendicular Recording drives operate in ‘‘Extra High Den-
sity’’ mode at 1 Mb s and are downward compatible with
1 44 Mbyte and 720 kbyte drives at 500 kb s (High Density)
and 250 kb s (Double Density) respectively If perpendicular
drives are present in the system this command should be
issued during initialization of the floppy controller which will
configure each drive as perpendicular or conventional
Then when a drive is accessed for a Format or Write Data
command the floppy controller will adjust the Format or
Write Data parameters based on the data rate (see Table
4-4)
Looking at the second command byte DC3– DC0 corre-
spond to the four logical drives A ‘‘0’’ written to DCn sets
drive n to conventional mode and a ‘‘1’’ sets drive n to
perpendicular mode Also the OW (Overwrite) bit offers ad-
ditional control When OW
DC3– DC0 (drive configuration bits) is enabled When
OW
regardless of what is written to DC3– DC0
The function of the DCn bits must also be qualified by set-
ting both WG and GAP to 0 If WG and GAP are used (i e
not set to 00) they will override whatever is programmed in
the DCn bits Table 4-4A indicates the operation of the
PC8477B based on the values of GAP and WG Note that
when GAP and WG are both 0 the DCn bits are used to
configure each logical drive as conventional or perpendicu-
lar DC3– DC0 are unaffected by a software reset but WG
and GAP are both cleared to 0 after a software reset A
hardware reset will reset all the bits to zero (conventional
mode for all drives) The Perpendicular Mode command bits
may be rewritten at any time
Note When in the Perpendicular Mode for any drive at any data rate via the
1
e
e
DC3–DC0 bits write precompensation is set to zero
NSC command
Enable the MFM output to act as the active low out-
put of the Data Separator charge pump This signal
consists of a series of pulses indicating when the
phase comparator is making a phase correction
This Pump output will be active low for a pump up or
pump down signal from the phase comparator and
is intended as a test mode to aid in the evaluation of
the Data Separator
0 the internal values of DC3– DC0 are unaffected
e
1 changing the values of