Flag Register (Flg); Bit 0: Carry Flag (C Flag); Bit 1: Debug Flag (D Flag); Bit 2: Zero Flag (Z Flag) - Renesas R8C/Tiny Series Software Manual

Chapter 1 Overview

1.4 Flag Register (FLG)

Figure 1.4.1 shows a configuration of the flag register (FLG). The function of each flag is detailed below.

1.4.1 Bit 0: Carry flag (C flag)

This flag holds a carry, borrow, or shifted-out bit that has occurred in the arithmetic/logic unit.

1.4.2 Bit 1: Debug flag (D flag)

This flag enables a single-step interrupt.
When this flag is set (= 1), a single-step interrupt is generated after an instruction is executed. When an
interrupt is acknowledged, this flag is cleared to 0.

1.4.3 Bit 2: Zero flag (Z flag)

This flag is set when an arithmetic operation resulted in 0; otherwise, this flag is 0.

1.4.4 Bit 3: Sign flag (S flag)

This flag is set when an arithmetic operation resulted in a negative value; otherwise, this flag is 0.

1.4.5 Bit 4: Register bank select flag (B flag)

This flag selects a register bank. If this flag is 0, register bank 0 is selected; if the flag is 1, register bank
1 is selected.

1.4.6 Bit 5: Overflow flag (O flag)

This flag is set when an arithmetic operation resulted in overflow.

1.4.7 Bit 6: Interrupt enable flag (I flag)

This flag enables a maskable interrupt.
When this flag is 0, the interrupt is disabled; when the flag is 1, the interrupt is enabled. When the
interrupt is acknowledged, this flag is cleared to 0.

1.4.8 Bit 7: Stack pointer select flag (U flag)

When this flag is 0, the interrupt stack pointer (ISP) is selected; when the flag is 1, the user stack pointer
(USP) is selected.
This flag is cleared to 0 when a hardware interrupt is acknowledged or an INT instruction of software
interrupt numbers 0 to 31 is executed.

1.4.9 Bits 8-11: Reserved area

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1.4 Flag Register (FLG)