38
MITSUBISHI MICROCOMPUTERS
7477/7478 GROUP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
PROM READING AND WRITING
Reading
To read the PROM, set the CE and OE pins to “L” level. Input the
address of the data (A
0
to A
14
) to be read and the data will be out-
put to the I/O pins (D
0
to D
7)
. The data I/O pins will be floating
when either the CE or OE pin is in the “H” state.
Writing
To write to the PROM, set the OE pin to “H” level. The CPU will en-
ter the program mode when V
PP
is applied to the V
PP
pin. The
address to be written to is selected with pins A
0
to A
14
, and the
data to be written is input to pins D
0
to D
7
. Set the CE pin to “L”
level to begin writing.
Note on Writing
When using a PROM programmer, the address range should be
between 4000
16
and 7FFF
16
. When data is written between ad-
dresses 0000
16
and 7FFF
16
, fill addresses 0000
16
to 3FFF
16
with
FF
16
.
Erasing
Data can only erased on the M37478E8SS ceramic package,
which includes a window. To erase data on this chip, use an ultra-
violet light source with a 2537 Angstrom wave length. The
minimum radiation power necessary for erasing is 15W·s/cm
2
.
Writing with PROM programmer
Verify test with PROM programmer
Function check in target device
Screening (Caution) (Leave at 150
°
C for 40 hours.)
Caution : Since the screening temperature is higher than storage
temperature, never expose to 150°C exceeding 100
hours.
Read-out
Output disable
Programming
Programming verify
Program disable
Note :
V
IL
and V
IH
indicate an “L” and an “H” input voltage, respectively.
Output
Floating
Input
Output
Floating
V
IL
V
IH
V
IH
V
IL
V
IH
V
CC
V
CC
V
PP
V
PP
V
PP
V
CC
V
CC
V
CC
V
CC
V
CC
V
IL
V
IL
V
IL
V
IH
V
IH
Pin
Mode
CE
OE
V
PP
V
CC
Data I/O
Table 3. I/O signal in each mode
NOTES ON HANDLING
(1) Sunlight and fluorescent light contain wave lengths capable of
erasing data. For ceramic package types, cover the transpar-
ent window with a seal (provided) when this chip is in use.
However, this seal must not contact the lead pins.
(2) Before erasing, the glass should be cleaned and stains such
as finger prints should be removed thoroughly. If these stains
are not removed, complete erasure of the data could be pre-
vented.
(3) Since a high voltage (12.5V) is used to write data, care should
be taken when turning on the PROM programmer’s power.
(4) For the programmable microcomputer (shipped in One Time
PROM version), Mitsubishi does not perform PROM write test
and screening in the assembly process and following pro-
cesses. To improve reliability after write, performing write and
test according to the flow below before use is recommended.