Intel MCS48 User Manual page 168

ID8048/8748/8035L
CRYSTAL OSCILLATOR
MODE
DRIVING
FROM
EXTERNAL
SOURCE
0—
15
pF
(INCLUDES XTAL
^
SOCKET, STRAY)
-o
15-25
pF
=£
(INCLUDES SOCKET,
STRAY)
-±
CRYSTAL
SERIES RESISTANCE SHOULD
BE <75S AT
6
MHz; <180S
AT
3.6
MHz.
BOTH
X1
AND
X2
SHOULD
BE DRIVEN.
RESISTORS
TO
Vcc
ARE NEEDED TO ENSURE
V|
H
=
3.8V
IF
TTL CIRCUITRY
IS
USED.
THE MINIMUM
HIGH
AND
THE MINIMUM
LOW
TIMES
ARE
45%.
LC
OSCILLATOR
MODE
45 mH 20
pF
120
M
H
20 pF
2n<fLC
C
PP
=
5-10pF
PINTO-PIN
CAPACITANCE
EACH C
SHOULD
BE
APPROXIMATELY
20 pF,
INCLUDING STRAY CAPACITANCE.
PROGRAMMING,
VERIFYING,
AND
ERASING THE
8748
EPROM
Programming
Verification
In brief,
the
programming process consists
of:
activat-
ing
the
program mode,
applying an address, latching the
address, applying
data,
and
applying a
programming
pulse.
Each word
is
programmed completely before
moving on
to the next
and
is
followed by a
verification
step.
The
following
is
a
list
of
the pins used
for
program-
ming and
a description of their functions:
Pin
Function
XTAL1
Clock
Input
(1
to 6
MHz)
RESET
Initialization
and Address Latching
TEST
Selection
of
Program
or Verify
Mode
EA
Activation of
Program/Verify
Modes
BUS
Address and
Data Input
Data Output during
Verify
P20-1
Address
Input
V
D d
Programming Power Supply
PROG
Program Pulse Input
WARNING:
An
attempt
to
program
a
mis-socketed 8748
will
result in
severe
damage
to
the
part.
An
indication of
a properly
socketed
part
is
the
appearance
of the
ALE
clock
out-
put.
The
lack of this
clock
may
be used
to
disable the
programmer.
The
Program/Verify
Sequence
is:
1.
V
DD
=
5V, cloc k
applied or
internal oscillator
oper-
ating,
RESET
=
0V,
TEST =
5V,
EA =
5V,
BUS
and
PROG
floating.
2.
Insert
8748
in
programming
socket.
3.
TEST = 0V
(select
program mode).
4.
EA =
23V
(activate
program mode).
5.
Address
applied
to
BUS
and
P20-1.
6.
RESET =
5V
(latch
address).
7.
Data applied
to
BUS.
8.
V
DD
=
25V (programming
power).
9.
PROG
= 0V
followed by
one
50
ms
pulse to 23
V.
10.
V
DD
=
5V.
11.
TEST =
5V
(verify
mode).
12.
Read and
verify
data on BUS.
13.
TEST0 =
0V.
14.
RESET =
0V and
repeat
from step
5.
15.
Programmer
should be
at
conditions
of
step
1
when
8748
is
removed from socket.
6-16