PC8477BV-1 National Semiconductor, PC8477BV-1 Datasheet - Page 27

• 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
4 2 15 Scan Commands
The Scan commands allow data read from the disk to be
compared against data sent from the
Scan commands to choose from
Each sector is interpreted with the most significant bytes
first If the Wildcard mode is enabled in the Mode command
an FF (hex) from either the disk or the P is used as a don’t
care byte that will always match equal After each sector is
read if the desired condition has not been met the next
sector is read The next sector is defined as the current
sector number plus the Sector Step Size specified The
Scan command will continue until the scan condition has
been met or the EOT has been reached or if TC is assert-
ed
Read errors on the disk will have the same error conditions
as the Read Data command If the SK bit is set sectors with
deleted data marks are ignored If all sectors read are
skipped the command will terminate with D3 of ST2 set
(Scan Equal Hit) The Result Phase of the command is
shown in Table 4-10
4 2 16 Seek Command
The Seek command issues step pulses to move the select-
ed drive head in or out until the desired track number is
reached During the Execution Phase of the Seek com-
mand the track number to seek to is compared with the
present track number The controller will determine how
many step pulses to issue and the DIR disk interface output
will indicate which direction the R W head should move
The DRx BUSY bit is set in the MSR for the appropriate
drive The controller will wait the Motor On time before issu-
ing the first step pulse
After the Motor On time the controller will enter the Idle
Phase The execution of the actual step pulses occurs in the
Drive Polling phase of the controller The step pulse rate is
determined by the value programmed in the Specify com-
mand An interrupt will be generated one step pulse period
after the last step pulse is issued There is no Result Phase
A Sense Interrupt command should be issued to determine
the cause of the interrupt
While the internal microengine is capable of multiple seeks
on 2 or more drives at the same time software should en-
sure that only one drive is seeking or recalibrating at a time
This is because the drives are actually selected via the
DOR which can only select one drive at a time No other
Scan Equal
Scan Low
or Equal
Scan High
or Equal
TABLE 4-10 Scan Command Termination Values
Command
Scan Equal
Scan Low or Equal
Scan High or Equal
D2
0
1
0
0
1
0
0
1
Register 2
Status
Disk Data
Disk Data
Disk Data
D3
1
0
1
0
0
1
0
0
e
s
t
P There are three
P Data
P Data
P Data
Conditions
Disk
Disk
Disk
Disk
Disk
Disk
Disk
Disk
e
e
e
i
k
l
k
l
(Continued)
P
P
P
P
P
P
P
P
27
command except a Sense Interrupt command should be is-
sued while a Seek command is in progress
If the extended track range mode is enabled with the ETR
bit in the Mode command a fourth command byte should be
written in the Command Phase to indicate the four most
significant bits of the desired track number Otherwise only
three command bytes should be written
4 2 17 Sense Drive Status Command
The Sense Drive Status command returns the status of the
selected disk drive in ST3 This command does not gener-
ate an interrupt
4 2 18 Sense Interrupt Command
The Sense Interrupt command is used to determine the
cause of interrupt when the interrupt is a result of the
change in status of any disk drive Four possible causes of
the interrupt are
1 Upon entering the Result Phase of
2 During data transfers in the Execution Phase while in the
3 Ready Changed State during the polling mode for an in-
4 Seek Relative Seek or Recalibrate termination
An interrupt due to reasons 1 and 2 does not require the
Sense Interrupt command and is cleared automatically This
interrupt occurs during normal command operations and is
easily discernible by the
cleared reading or writing information from to the Data Reg-
ister (FIFO)
Interrupts caused by reason 3 and 4 are identified with the
aid of the Sense Interrupt command The interrupt is cleared
after the first result byte has been read Use bits 5 6 and 7
of ST0 to identify the cause of the interrupt as shown in
Table 4-11
Issuing a Sense Interrupt command without an interrupt
pending is treated as an Invalid command If the extended
track range mode is enabled a third byte should be read in
the Result Phase which will indicate the four most signifi-
cant bits of the present track number Otherwise only two
result bytes should be read
a Read Data command
b Read Deleted Data command
c Read a Track command
d Read ID command
e Write Data command
f Write Deleted Data command
g Format command
h Scan command
i Verify command
Non-DMA mode
ternally selected drive (Occurs only after a hardware or
software reset )
D7
Interrupt
1
0
0
TABLE 4-11 Status Register 0 Termination Codes
Status Register 0
Code
D6
1
0
1
Seek
End
D5
0
1
1
P via the MSR This interrupt is
Internal Ready Went True
Normal Seek Termination
Abnormal Seek Termination
Cause