Intel MCS48 User Manual page 435

EM1
HARDWARE
The EM1
emulation board uses
the
8748
to
perform the
emulation.
PO
Simulator
Port
of
the 8021
is
a
quasi-bidirectional* port.
The PO
simulator converts the
data bus
of
the
8748
into a
quasi-
bidirectional port.
Crystal
Control Clock
Buffer
The EM1
allows the user
to select
an on-board oscillator
or a
TTL
clock driven
from the 8021 user's prototype
system
via a
Cambion
Suitcase jumper.
Jumper
W1
Position
A-B
C-D
State
On-Board
External
TTL
Clock
*A
bidirectional port
which
serves as
an input
port,
output
port,
or both,
even though outputs
are statically latched.
Zero Cross Detection Simulator
The
zero
cross detection simulator enables the 8748's
T1 input to
detect zero-crossings.
The
circuitry
provides
a high
level
signal
on
a positive
crossing
and
a
low
level
signal
on a negative crossing of
zero
to
the T1 input of
the 8748.
Reset
Buffer
The
8021 resets
on
a logic
HIGH
level
signal.
However,
the
8748 resets
on
a
logic
LOW
level,
thus an
inverter
is
provided
on
the
MDS-EM1
to
make
the
two
chips
com-
patible.
Optional Pull
Ups
Resistors are provided
to
simulate the optional pull-up
resistors
on
T1 input
and
port of
the 8021.
A
removable
resistor
pack
is
used on
port
0.
The
T1 input pull
up can
be installed
by soldering
in
a
50K
resistor.
SOFTWARE
When
emulating the 8021 with
observe the 8021
instruction set.
EM1
the user
must
40
LINES
CABLE TO
ICE-49
8748
OR
40-PIN
PLUG
^>
PORT /-
SIMULATOR y-
P10-P17
P20-P28
CRYSTAL
CONTROL
CLOCK
CROSSING
DETECTION
SIMULATORS
|
OPTIONAL
I
|
PULL UP
I
I I
It
<3
}
RESET BUFFER
8021
CABLE
PLUG
28
LINES
12
INCHES
FLAT
CABLE
J___
ON CARD
CLOCK
i
'
OPTION
j
28-PIN
,
J
n
SOCKET
|
OPTIONAL
I
PULL UP
!
L
J
EM1 FUNCTION
DIAGRAM
9-21