UPD765 Просмотр технического описания (PDF) - NEC => Renesas Technology
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UPD765 Datasheet PDF : 17 Pages
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uPD765A/uPD765B
NEC
Table 3. Status Register Identification
Pin
NO.
Name
Function
Status Register 0
D7, D6 IC
(Interrupt Code)
D7=0 and D6=0
Normal termination of command, (NT)
Command was completed and properly ex-
ecuted
D7=0 and D6=1
Abnormal termination of command, (AT)
Execution of command was started but
was not successfully completed.
D7=1 and D6=0
Invalid command issue, (IC) Command
which was issued was never started
D7=1 and D6=1
Abnormal termination because during
command execution the ready srgnal from
FDD changed state
D65 S E
(Seek End)
When the FDC completes the Seek com-
mand, this flag IS set lo 1 (high).
D4
EC
If a fault srgnal IS received from the FDD, or
(Equipment Check) if the track 0 srgnal fails to occur after 77
step pulses (Recalibrate Command) then
this flag is set
D3 N R
(Not Ready)
When the FDD IS in the not-ready state and
a Read or Write command IS Issued, this
flag IS set If a Read or Write command is
issued to side 1 of a single-sided drive,
then this flag IS set
D2 H D
(Head Address)
This flag IS used to indicate the state of the
head at interrupt.
D1 US:
(Unit Select 1)
This flag IS used to indicate a drive unit
number at interrupt.
D0 Us0
(Unit Select 0)
This flaa is used to Indicate a drive unit
number at interrupt
Status Register 1
D7 EN
(End of Cylinder)
When the FDC tries to access a sector be-
yond the final sector of a cylinder, this flag
IS set
Not used. This bit is always 0 (low)
DE(Data Error)
When the FDC detects a CRC(1) error in ei-
ther the ID field or the data field, this flag is
set
D4 OR
(Overrun)
If the FDC is not serviced by the host sys-
tem during data transfers within a certain
time interval. this flaa is set.
D3
Not used. This bit is alwavs 0 (low).
Table 3. Status Register Identification (cont)
Pin
NO.
Name
Function
Status Register 1 (cont)
D2 ND
(No Data)
During execution of Read Data. Read De-
leted Data Write Data. Write Deleted Data
or Scan command, if the FDC cannot find
the sector specified in the IDR(2)Register,
this flag is set.
During execution of the Read ID command.
if the FDC cannot read the ID field without
an error, then this flag IS set.
During execution of the Read Diagnostic
command. if the starting sector cannot be
found, then this flag is set.
D1
NW(Not Writeable)
During execution of Write Data, Write De-
leted Data or Write ID command. if the FDC
detect: a write protect srgnal from the
FDD. then this flag is Set
Do MA
(Missing Address
Mark)
This bit is set if the FDC does not detect the
IDAM before 2 index pulses It is also set if
the FDC cannot find the DAM or DDAM af-
ter the IDAM is found. MD bit of ST2 is also
ser at this time.
Status Register 2
D7
Not used. This bit IS alwavs 0 (low)
De CM
(Control Mark)
During execution of the Read Data or Scan
command, if the FDC encounters a sector
which contains a deleted data address
mark, this flag is set Also set if DAM is
found during Read Deleted Data
D5 DD
(Data Error in
Data Field)
If the FDC detects a CRC error in the data
field then this flag is set
DA W C
(Wrong Cylinder)
This bit IS related to the ND bit, and when
the contents of C(3) on the medium is dif-
ferent from that stored in the IDR. this flag
is set
D3 SH
(Scan Equal Hit)
During execution of the Scan command. if
the condition of “equal” is satisfied, this
flag is set.
D2 SN
During execution of the Scan command, if
(Scan N o t S a t i s f i e d ) the F D cannot find a sector on the cylin-
der which meets the condition. then Cthis
flag is set
D1
BC
(Bad Cylinder)
This bit is related to the ND bit. and when
the contents of C on the medium is differ-
ent from that stored in the IDR and the con-
tents of C IS FFH. then this flag IS set
Do MD
When data IS read from the medium, if the
(Missing Address FDC cannot find a data address mark or
Mark in Data Field) deleted data address mark, then this flag
is set
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