4570 Datasheet, PDF (11/69 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
4570 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER
(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 reference instruction (TABP p) is
executed.
Program counter consists of PCH (most significant bit to bit
7) which specifies to a ROM page and PCL (bits 6 to 0) which
specifies 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 PCH does not specify after the last page
of the built-in ROM.
Program counter (PC)
p6 p5 p4 p3 p2 p1 p0 a6 a5 a4 a3 a2 a1 a0
PCH
Specifying page
PCL
Specifying address
Fig. 7 Program counter (PC) structure
Data pointer (DP)
Z1 Z0 X3 X2 X1 X0 Y3 Y2 Y1 Y0
(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, register 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 or RD instruction (Figure 9).
Register Y (4) Specifying
RAM digit
Register X (4)
Specifying RAM file
Register Z (2)
Specifying RAM file group
Fig. 8 Data pointer (DP) structure
Specifying bit position
Set
0101
Register Y (4)
D9 D6 D5 D4 D0
1
Port D output latch
Fig. 9 SD instruction execution example
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