LCD-IV
• Program Counter (PC)
The program counter
is
used for addressing
of
ROM. The
program counter consists
of
the bank part, the page part, and
the address part
as
shown in Figure 2.
Bank
Page
Address
o
Page
P
L
1
Page
lJ
30
Page
31
Page
lL
L
3F
Address
3E Address
OF
Address
1F Address
3F
Address
3E Address
Bank
'-----
~:~---~
L-
____
:a~~ress
,art
I
L..
---(Page
Partl----'
Note: The parenthesized contents are expressions
of
the
Page,combining the bank part with the page part.
Figure 2 Configuration
of
Program
Counter
The bank part
is
a I-bit register and the page part
is
as-bit
register.
Table 1 Program
Counter
Address Part Sequence
Once a certain value
is
loaded into the bank part or the page
part, the content
is
unchanged until other value is loaded by a
program.
The settable value
is
"0"
(the
Bank
0)
or
"I"
(the Bank
I)
for the bank part, and 0
to
31
for the page part.
The address part
is
a 6-bit polynomial counter and counts up
for each instruction cycle time. The sequence in the decimal and
hexa-decimal system
is
shown in Table
1.
This sequence
is
cir-
culating and has neither the starting nor ending point.
It
doesn't
generate an overflow carry. Consequently,
the
program
on
a
same page is executed
in order unless the value
of
the bank part
or
the
page part
is
changed.
187
Decimal
63
62
61
59
55
47
30
60
57
51
39
14
29
58
53
43
22
44
24
48
33
2
Hexa-
Decimal
decimal
3F 5
3E
11
3D 23
38
46
37 28
2F
56
1E
49
3C
35
39
6
33
13
27 27
OE
54
10
45
3A
26
35
52
28
41
16 18
2C
36
18
8
30
17
21
34
02
4
Hexa-
Decimal
Hexa-
decimal
decimal
05
9
09
OB
19
13
17
38
26
2E
12
OC
1C 25
19
38
50
32
31
37
25
23
10
OA
06
21
15
00
42
2A
1B
20
14
36
40
28
20
16
10
1A
32
20
34
0
00
29
1
01
12
3
03
24 7
07
08
15
OF
11
31
1F
22
04
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