Renesas 4514 用户手册
4513/4514 Group User’s Manual
HARDWARE
1-19
FUNCTION BLOCK OPERATIONS
(8) Program counter (PC)
Program counter (PC) is used to specify a ROM address (page and
address). It determines a sequence in which instructions stored in
ROM are read. It is a binary counter that increments the number of
instruction bytes each time an instruction is executed. However,
the value changes to a specified address when branch instructions,
subroutine call instructions, return instructions, or the table refer-
ence instruction (TABP p) is executed.
Program counter consists of PC
H
(most significant bit to bit 7)
which specifies to a ROM page and PC
L
(bits 6 to 0) which speci-
fies an address within a page. After it reaches the last address
(address 127) of a page, it specifies address 0 of the next page
(Figure 7).
Make sure that the PC
H
does not specify after the last page of the
built-in ROM.
(9) Data pointer (DP)
Data pointer (DP) is used to specify a RAM address and consists
of registers Z, X, and Y. Register Z specifies a RAM file group, reg-
ister X specifies a file, and register Y specifies a RAM digit (Figure
8).
Register Y is also used to specify the port D bit position.
When using port D, set the port D bit position to register Y certainly
and execute the SD, RD, or SZD instruction (Figure 9).
Fig. 7 Program counter (PC) structure
Fig. 8 Data pointer (DP) structure
Fig. 9 SD instruction execution example
Z
1
Z
0
X
3
X
2
X
1
X
0
Y
3
Y
2
Y
1
Y
0
Data pointer (DP)
Register Z (2)
Register X (4)
Register Y (4)
Specifying
RAM digit
RAM digit
Specifying RAM file
Specifying RAM file group
0
1
0
1
1
D
7
Set
Specifying bit position
Port D output latch
Register Y (4)
D
5
D
6
D
4
D
0
p
5
p
4
p
3
p
2
p
1
p
0
a
6
a
5
a
4
a
3
a
2
a
1
a
0
Program counter
PC
H
Specifying page
PC
L
Specifying address
p
6