Intel MCS48 User Manual page 172

M8048/M8748/M8035
CRYSTAL OSCILLATOR
MODE
DRIVING
FROM
EXTERNAL
SOURCE
0-
15pF
(INCLUDES XTAL, -i-
SOCKET, STRAY)
1-6
mHz
CZI
15-25
pF
^
(INCLUDES SOCKET,
STRAY)
-±
CRYSTAL
SERIES RESISTANCE
SHOULD
BE <75« AT
6
MHz,
<180S2 AT3.6
MHz
-o
BOTH
X1
AND
X2 SHOULD BE DRIVEN.
RESISTORS TO
Vcc
ARE NEEDED TO ENSURE
Vih
= 3.8V
IF
TTL CIRCUITRY
IS
USED.
THE MINIMUM
HIGH
AND THE MINIMUM LOW
TIMES
ARE
45%.
LC
OSCILLATOR
MODE
45
M
H 20 pF
5.2
MHz
120
M
H
20
pF
3.2
MHz
1
2n^LC
C + 3Cpp
C =
Cpp =
5-10
pF
PIN-TO-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:
activating
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
follow-
ing
is
a
list
of the pins used
for
programming and
a
descrip-
tion of their functions:
Pin
Function
XTAL1
Clock Input
(1
to6MHz)
Reset Initialization
and Address Latching
TestO
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
missocketed
8748
will result
in
severe
damage
to the
part.
An
indication of
a
properly socketed part
is
the
appearance of the
ALE
clock output.
The
lack of this
clock
may
be
used to disable the
programmer.
The
Program/Verify sequence
is:
1.
Vpp
=
5v,
Clock
applied or
internal oscillator
operating,
RESET
=
Ov,
TEST
=
5v,
EA
=
5v,
BUS
and
PROG
floating.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Insert
8748
in
programming
socket
TEST
= Ov
(select
program mode)
EA
= 23V
(activate
program mode)
Address applied to
BUS
and P20-1
RESET
= 5v
(latch address)
Data applied
to
BUS
Vqq
= 25v (programming power)
PROG
=
Ov followed by one
50ms
pulse to
23V
V
DD
= 5v
TEST
= 5v
(verify
mode)
Read and
verify
data
on
BUS
TEST
=
Ov
RESET
=
Ov and
repeat
from
step
5
Programmer should be
at
conditions
of step
1
when 8748
is
removed from
socket.
6-20