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Explanation Of Lsi - Sharp MZ1F10 Service Manual

Hard disk interface
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7.
EXPLANATION OF LSI
7-1. NDC840
1)GENERAL
NDC840 is a highly integrated one-chip Hard Disk Control-
ler (HOC). This high-speed controller uses a dual buffer.
A DMA con
t
roller is built in HOC.
FEATURES
Transfer Rate between HOC and a Hard Disk Drive
(HOD)
20 Mbits/s
Buffer
DMA
Dual buffer ava ilable
DMA controlle
r
in HOC
Transfer Rate between Host and HOC
DMA dual= 2.3MB/s (max)
Data check, Correction
CRC or ECC (11 bit burst correction)
Drive 1/F
SMD 1/F or Floppy 1/F
Data Bus
Dynamic Memory
Power Supply
8-bit t imign signal bidirection
Refresh timing signal bidirection
+5VDC
2) APPLICATIONS
2)-1. Main Memory Direct Transfer
H
O
MAIN~=~
~
MEMORY
Main Memory
When a Main-Memory cycle time can follow up a disk
transfer rate, data can be transferred directly into the
Main Memory
.
(1) Main-Memory cycle time (Byte Transfer)
10
6
0
.
k T
f
R
(b.
I
)x 8 Memory Cycle Time (J.LS)
ts
rans er
ate
tt s
2)-2. Single-Buffer Transfer
H
0
s
T
PROGRAM
EJ
RAM
(1) RAM
HOC PROGRAM area
*BUF
=
BUFFER
BUF
:
1 SECTOR or 1 TRACK BUF
(2) HOST, BUF Transfer Rate
-
M Z
-
5600A
When data are transferred between the
5"
FXD and
host,
data shall be accomdated temporarily in a buffer register.
Transfers can be executed at any t ransfer rate.
(3) BUF area
A buffer area can be allocated as one area of Main
Memory,
2)-3. DUAL-BU F Transfer
(1) RAM
P~M
6
(RAM)
HOC PROGRAM area
BUF
0,
BUF 1 area
Either BUF is a 1 SECTOR BUF.
2KB/CHIP RAM - max imum SECTOR length= 512 Bytes
A buffer transfers data in time-sharing.
(2) HOST, BUF Transfer Rate
When data are transferred between the
5"
F XD and host,
data shall
be
accomodated temporarily in a buffer
register.
Transfers can be executed at any transfer rate
.
In multisectors, transfer rates of the host and buffer
deter-
mine sector interleaves.
3) TRANSFER MODES
3)-1. Single Buffer
DMA shall be transferred regardless of the disk transfer
rate
.
The hardware of the host shall become Japanese.
Host cycle-steal and prior interruption.
In a multi -sector mode, process efficiency
decreases.
(e.g .) READ DATA
(DISK~
HOST)
~~!~,\T
I
SECTOR
1
I
n SECTOR interleave
I
SECTOR
21
D
ATA
-
15
-
l:iECTOil
I
DATA
S
E<.:TOU 2 DATA
lDil:iK-
BUJ-'
l:iECTOH I DATA
BUF
-
HO
S
T
Sector interleaves need
t ime for buffer - host
transfer
.
l!ll:iK-
BUJ-'
SECTOR 2
DATA
BUJ-'
-HOl:iT

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