Mcu Scu; Mcu And Scu Operations - JUKI 6100 Technical Manual

7.2
MCU
and
SCU
Operations
Within the
6100
there are
two
printed circuit
boards
which monitor and control
all
of the printers functions.
The two
boards
are the
Master Control Unit
(MCU-1)
and
the Slave
Control Unit (SCU-1).
The
Master Control Unit,
running
a
ROM
resident control
program,
receives
data via the parallel
interface
from
the
Host
CPU,
returns
handshake
signals to
the interface, stores
data
and
escape sequences
in
memory
and
passes data
and control
signals to
the
SCU
The
MCU
also
monitors
the
Operator Panel functions.
The
SCU
board
receives the data
and
control
signals
from
the
MCU
and performs
the actual tasks
of
head
positioning,
daisywheel
positioning,
etc.
The
SCU
operates
under control of
its
own Masked
ROM
pro-
gram which
is
an
internal
portion of the
SCUs
microprocessor.
A
third circuit
board (MCU-2),
which
is
a
Serial
Interface
Option, can be
installed
onto
the
MCU-1
board to provide
RS-232 communications capability. Installation
of
this
option
over-rides
the standard
parallel interface.
The
MCU-1
board
is
comprised of
a
microprocessor (either
an
803
1
or
and 805
1),
a
control
ROM,
an
8155
PIA, 2
to
8K
of
RAM
and
associated
support
circuitry.
Fig.
7.11
is
an
illustraction
of the
8155 and the various I/O
and
control
lines
which connect
to
it.
The 8155
consists
of an
internal
256 byte
RAM,
which
the
microprocessor uses for
a
scratchpad
memory,
a
programmable
14
bit
timer with
mode
control,
two
8 bit
bidirectional
ports (port
A
and port B)
and
a bidirectio-
nal
6
bit
port (port C)
which can be used for control functions.
Port
C
is
set
to
what
is
known
as
"ALT
3"
mode
during initialization
of
the printer. Bits 0,1
and
2
of port
C
become
control
lines
which
are
used
in
conjuntion with port A. Port
A
is
used
as
an input buffer
from
the parallel interface.
Port
C
bit 2
is
used for the
incoming
strobe
line, bit
1
is
used to indicate a
busy
condition
and
bit
0
is
used
to
initiate
an interrupt to the
8031/805
1
MPU.
The
remaining three
bits
of port
C
are
used for
the following
:
bit
3
-
drives the
READY
lamp on
the
Operation
Panel,
bit
4
-
drives
the
CHECK
lamp and
bit 5
is
used to drive
the audible alarm.
Port
B
bits 0,
1
and
2 are
used
for
reading the condition of the front panel
switches during the initialization
sequence. Port
B
bits 3, 4,
and
5 are
used
for
reading the condition of the
serial
interface
board switches
if
this
option
is
installed.
Port
B
bit
6
is
used
to indicate to
the
microprocessor
whether
or
not the
serial
interface
board
is
present.
The Timer
In
and Timer Out
lines are
used
solely
for the
serial
interface.
The
transfer
of data
between
the
8155 and
the
8031/8051
takes place
over the multiplexed
Address/Data
lines
(ADO ~
AD7). The
Address
Latch Enable
(ALE)
line
indicates
when
there
is
a valied
address
on
the address/
data
lines
and
the
Memory/IO
line selects
whether
the bidirectional data
will
be
sent to/received
from
the internal
RAM,
the timer or
one of
the ports.
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