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參數(shù)資料
| 型號(hào)： | UPD765A |
| 廠商： | NEC Corp. |
| 英文描述： | Single/Double Density Floppy-Disk Controller |
| 中文描述： | 單/雙密度軟盤控制器 |
| 文件頁數(shù)： | 11/17頁 |
| 文件大?。?/td> | 344K |
| 代理商： | UPD765A |
uPD765A/uPD765B
NEC
Table 3. Status Register Identification
(cont)
Pin
NC.
Name
Status Register 3
D7
FT
(Fault)
D6
WP
(Write Protected)
D56
RY
(Ready)
D4
TO
(Track 0)
03
TS
(Two-Side)
D2
HD
(Head Address)
Command Symbol Description
Name
A0
(Address
Line
0)
C
(Cylmder Number)
D
(Data)
D7-D0
(Data Bus)
DTL
(Data Length)
Function
A0
controls
selection
of
main
status
register
(A0=0)
or data
register (A0=
1).
C stands for the current /selected
cylinder
(track) numbers 0 through 76 of the medium
D stands for the data pattern
which
is going to be
written into a sector
during
WRITE ID
operation
8-bit
data bus, where D7 stands for a most
significant
bit,
and
D0
stands for a least
significant
bit.
When N is defined as 00. DTL stands for the data
length which users are
going
to read out or
write
into
the sector
EOT stands for the
final
sector number on a
cylin-
der Durmg read or
write operations,
FDC will
stop
data transfer after a sector number
equal
to EOT
GPL stands for the length of gap 3.
During
Read
/
Write commands
this
value determnes the num-
ber of bytes that VCO sync
will
stay
low
after two
CRC bytes
During
Format command
it
deter-
mines
the
size
of gap 3
H stands for the
logical
head number 0 or 1. as
specified
in ID field
Function
This bit is used to indicate the status of the
fault
signal
fromthe FDD.
This bit is used to indicate the status of the
write protected signal fromthe FDD.
This
bit is used to Indicate the status of the
ready signal fromthe FDD.
This bit
IS
used to
indicate
track 0 signal fromthe
FDD.
the
status of
the
This
bit
used to indicate the status of the
two-side signal fromthe FDD.
This bit is used to Indicate the
side select signal to the FDD
This
bit is used to Indicate the status of the
unit select 1
signal
to the FDD.
This
bit is used to indicate the status of the
unit
select 0 signal to the FDD.
status
of
the
EOT
(End of Track)
D1
US1
(Unit Select
1)
D0
US0
(Unit Select 0)
Note:
(1) CRC
=
Cyclic Redundancy Check
(2)
IDR =
Internal Data Register
(3) Cylinder (C) is described more fully in the Command Symbol
Description.
GPL
(Gap Length)
HD
stands for a the physical head number 0 or
1
and controls the
polarity
of
pin
27 (H
=
HD in
all
command words
)
HLT stands for the head load time
in
the FDD (2
to
254 ms
in
2 ms Increments).
HUT stands for the head unload
time after a
Read
or
Write operation
has occurred (16 to
240
ms in
16 ms Increments)
H
(Head
Address)
HD(Head
Command
S equenc e
The
uPD765A/uPD765B
ferent commands. Each command is initiated by a
multibyte transfer from the processor, and the result af-
ter execution of the command may also be a multibyte
transfer back to the processor. Because of this
multi-
byte interchange of information between the
uPD765A/
uPD765B
and the processor, it is convenient to consider
each command as consisting of three phases:
Command
Phase:
quired to perform a particular opera-
tion from the processor.
The FDC performs the operation it
was instructed to do.
After completion of the operation,
status and other housekeeping infor-
mation are made available to the
processor.
is capable of performing 15 dif-
HLT
(Head Load
Time)
HUT
(Head Unload
Time)
If
MF
IS
low, FM mode
IS
selected, and if
it is high,
MFM mode
IS
selected
IF MT
is
high, a
multitrack operation
IS
per-
formed If MT = 1 after
finishing
read/write
oper-
ation
on
siude
0. FDC will
automatically
searching for sector 1 on side 1
MF
(FMor MFMMode)
M T
(Multitrack)
start
Execution
Phase:
Result Phase:
The FDC receives all information re-
N
(Number)
N stands for the number of data bvtes written
in
a
sector
NCN stands for a new
cylinder
number
which
going
to be reached as a result of the seek
opera-
tion;
desired
position
of head
ND stands for
operation
in
the non-DMA mode
N C N
(New
Cylinder
Number)
is
N D
(Non-DMA Mode)
P C N
(Present Cylinder Number) completion of Sense Interrupt Status command,
position
of head at
present
time
PCN stands for the cylinder number at the
Table 4 shows the required preset parameters and
results for each command. Most commands require 9
command bytes and return 7 bytes during the result
phase. The
“W”
to the left of each byte indicates a com-
mand phase byte to be written, and an “R” indicates a
result byte. The definitions of other abbriviations used
in table are given in the Command Symbol Description
table.
R
[Record)
R/W
(Read/Write)
S C
(Sector)
S K
(Skip)
R
stands for the sector number
which
or written
will
be read
R/W stands for either Read (R) or Write (W)
signal
SC indicates the number of sectors per
cylinder
SK stands for
skip
deleted data address mark
5-13
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