Processor Registers; Control Registers; Program Counter Format; Program Status Word Format - NEC PD78056F User Manual

Pd78058f series; pd78058fy series 8-bit single-chip microcontrollers

Table of Contents

5.2 Processor Registers

The PD78058F and 78058FY Subseries units incorporate the following processor registers.

The control registers control the program sequence, statuses and stack memory. The control registers consist

of a program counter (PC), a program status word (PSW) and a stack pointer (SP).

(1) Program counter (PC)

The program counter is a 16-bit register which holds the address information of the next program to be

In normal operation, the PC is automatically incremented according to the number of bytes of the instruction

to be fetched. When a branch instruction is executed, immediate data and register contents are set.

RESET input sets the reset vector table values at addresses 0000H and 0001H to the program counter.

PC13 PC12 PC11

(2) Program status word (PSW)

The program status word is an 8-bit register consisting of various flags to be set/reset by instruction execution.

Program status word contents are automatically stacked upon interrupt request generation or PUSH PSW

instruction execution and are automatically reset upon execution of the RETB, RETI and POP PSW instructions.

RESET input sets the PSW to 02H.

CHAPTER 5 CPU ARCHITECTURE

Figure 5-7. Program Counter Format

Figure 5-8. Program Status Word Format