a12 in
a7 in
a6 in
a5 in
a4 in
a3 in
a2 in
a1 in
a0 in
d0 out
d1 out
d2 out gnd v pp v dd 1
2
3
4
5
6
7
8
9
10
11
12
13
14 28
27
26
25
24
23
22
21
20
19
18
17
16
15 a14 in
a13 in
a8 in
a9 in
a11 in
oe in
a10 in
ce in
d7 out
d6 out
d5 out
d4 out
d3 out 10
9
8
7
6
5
4
3
25
24
21
23
2
26
27 11
12
13
15
16
17
18
19 ce oe a14
a13
a12
a11
a10
a9
a8
a7
a6
a5
a4
a3
a2
a1
a0 27
26
2
23
21
24
25
3
4
5
6
7
8
9
10 20 22 row
decoder column
decoder 262,144-bit
cell matrix column gate output buffer ce, oe
logic d0
d1
d2
d3
d4
d5
d6
d7 11
12
13
15
16
17
18
19
a0
a1
a2
a3
a4
a5
a6
a7
a8
a9
a10
a11
a12
a13
a14 d0
d1
d2
d3
d4
d5
d6
d7 a0 - a14
ce
d0 - d7
oe
v pp : address inputs
: chip enable input
: data outputs
: output enable input
: program power supply ce
oe 20
22 MBM27C256A(1/2)
il00 c-mos 256 k (32 k x 8)-bit uv erasable prom with 3-state outputs
?op view
an
an
an
x
an
an
an
x
ao ce
0
0
1
0
1
0
1
0 oe
0
1
x
1
0
0
1
0 v dd
+ 5 v
+ 5 v
+ 5 v
+ 6 v
+ 6 v
+ 6 v
+ 6 v
+ 5 v
v pp
+ 5 v
+ 5 v
+ 5 v
+ 12.5 v
+ 12.5 v
+ 12.5 v
+ 12.5 v
+ 5 v dn
d out
hi-z
hi-z
d in
d out
d out
hi-z
device code function
read
output disable
standby
pgm
pgm verify (1)
pgm verify (2)
pgm inh
electronic signature *
* see following description electronic signature for p rom writer
address settings in read mode maker code
device code ao
0
1
a1 - a8 a9 d7
0
0 a10 - a13 a14, vpp 0 12 v 0 1
code data d6
0
1 d5
0
1 d4
0
0 d3
0
0 d2
1
0 d1
0
1 d0
0
0
04h
62h MBM27C256A (2/2) 0
1
x hi-z : low level
: high level
: don? care
: high impedance
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