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MCS-85™ APPLICATIONS
Small System
Block Move, Block Search
The schematic
in
Figure 3
is
of a complete
microcomputer with only 6 ICs. The system con-
tains its own serial
1/0
communication lines,
multi-level
interrupt, two programmable timers,
and power-on reset.
System capacity
is
512
bytes of RAM, 4K bytes of
PROM, and
76
lines
of programmable
1/0.
In
a large system application high speed block
moves may
be
necessary. The addition of
an
8257 Direct Memory Access (DMA) controller
and
an
8255 Programmable Peripheral Interface
(PPI) device with some miscellaneous logic
removes the task from the' 8085 and results
in
a
very high speed capability. The addition of
an
eight bit comparator also permits block sear-
ches. (See Figure
4.)
-----+-
T
RAP
_ RST7,5
- RST6,5
--..
INTR
AD
DR
ADDR/DATA
181 181
8212
l~
DS1) -
Vss
Vcc
~
~
RESET
IN
HOLD
HlDA
SOD
8085A
SID
S1
RESET
OUT
So
ALE
AD
WR
101M
ROY
elK
'~
I
3TO
8
I
DECODER
I
I~
19
I~
15
.....--t---t--
..
IREADy
ORO
--------,
.....--t-+--I--I--__+_liOW
..__/----1
ClK
+-t-+-+-+-+--
__
IMEMW
'-'-'+--+--+--.-1
RESET
.-.-.+--+--+--+-+--11--1-----1
MEMR
.-.-.+--+--+-
__
RESET
+-t-+-t-----+-IWR
+-t-+-+-+-t-------IAD
o
DACK--
1 ORO
I-.----t---------.
DACK
____
2
ORO
I-.---t--t-----,
L>ACK -
PAt:(8~~P-
8BIT
COMPo
PB
18~
/ B
8255
- V
~~
FIGURE
4.
BLOCK MOVE, BLOCK SEARCH addition of
an
8257 Direct Memory Access (DMA)
con-
troller
and
an
8255 Programmable Peripheral Interface
(PPI)
device permits block searches, high
speed
block moves. (2.5
I1s/word).
A1-6
!
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