sub.c File Reference

Helper functions for subtraction operations. More...

#include "sub.h"
#include "utils.h"

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Functions
static void	___sub8_set_carry_flag (uint8_t a, uint8_t b, struct z80 *cpu)
	sets the carry flag based on the provided operands More...
static void	___sub8_set_zero_flag (uint8_t a, uint8_t b, struct z80 *cpu)
	sets the zero flag based on the provided operands More...
static void	___sub8_set_overflow_flag (uint8_t a, uint8_t b, struct z80 *cpu)
	sets the overflow flag based on the provided operands More...
static void	___sub8_set_sign_flag (uint8_t a, uint8_t b, struct z80 *cpu)
	sets the sign flag based on the provided operands More...
static void	___sub8_set_half_carry_flag (uint8_t a, uint8_t b, struct z80 *cpu)
	sets the half carry flag based on the provided operands More...
static void	__sub8_set_flags (uint8_t a, uint8_t b, struct z80 *cpu)
	wrapper to set flags based on the operands of a subtraction operation More...
void	_cp (uint8_t *reg, struct z80 *cpu)
	set flags as if operand was subtracted from A More...
void	_sub_a_reg8 (struct z80 *cpu, uint8_t *reg)
	subtracts reg from the A register More...
void	_sub_a_mem (struct z80 *cpu, uint8_t *memory)
	subtracts the contents of a memory address from the A register More...
void	_sbc_a_reg8 (struct z80 *cpu, uint8_t *reg)
	subtracts an 8-bit register from the A register with carry More...
void	_dec8 (uint8_t *n, struct z80 *cpu)
	decrements an 8-bit register More...

Detailed Description

Helper functions for subtraction operations.

Author

Peter H. Ezetta

Date

2018-2019

Function Documentation

___sub8_set_carry_flag()

static void ___sub8_set_carry_flag ( uint8_t  a, uint8_t  b, struct z80 *  cpu  )

static

sets the carry flag based on the provided operands

Parameters

a
b
cpu	z80 CPU object

___sub8_set_half_carry_flag()

static void ___sub8_set_half_carry_flag ( uint8_t  a, uint8_t  b, struct z80 *  cpu  )

static

sets the half carry flag based on the provided operands

Parameters

a
b
cpu	z80 CPU object

___sub8_set_overflow_flag()

static void ___sub8_set_overflow_flag ( uint8_t  a, uint8_t  b, struct z80 *  cpu  )

static

sets the overflow flag based on the provided operands

Parameters

a
b
cpu	z80 CPU object

___sub8_set_sign_flag()

static void ___sub8_set_sign_flag ( uint8_t  a, uint8_t  b, struct z80 *  cpu  )

static

sets the sign flag based on the provided operands

Parameters

a
b
cpu	z80 CPU object

___sub8_set_zero_flag()

static void ___sub8_set_zero_flag ( uint8_t  a, uint8_t  b, struct z80 *  cpu  )

static

sets the zero flag based on the provided operands

Parameters

a
b
cpu	z80 CPU object

__sub8_set_flags()

static void __sub8_set_flags ( uint8_t  a, uint8_t  b, struct z80 *  cpu  )

static

wrapper to set flags based on the operands of a subtraction operation

Parameters

a
b
cpu	z80 CPU object

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_cp()

void _cp	(	uint8_t *	reg,
		struct z80 *	cpu
	)

set flags as if operand was subtracted from A

Parameters

reg	register to subtract from A
cpu	z80 CPU object

The CP instruction sets the flags as if the operand to CP were subtracted from the A register, however the subtraction does not actually occur, and the original value of A is left untouched.

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_dec8()

void _dec8	(	uint8_t *	n,
		struct z80 *	cpu
	)

decrements an 8-bit register

Parameters

n	register to decrement
cpu	z80 CPU object

Bug:

dec8 isn't operating on flags

_sbc_a_reg8()

void _sbc_a_reg8	(	struct z80 *	cpu,
		uint8_t *	reg
	)

subtracts an 8-bit register from the A register with carry

Parameters

cpu	z80 CPU object
reg	register to subtract from A

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_sub_a_mem()

void _sub_a_mem	(	struct z80 *	cpu,
		uint8_t *	memory
	)

subtracts the contents of a memory address from the A register

Parameters

cpu	z80 CPU object
memory	pointer to memory to subtract from the A register

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_sub_a_reg8()

void _sub_a_reg8	(	struct z80 *	cpu,
		uint8_t *	reg
	)

subtracts reg from the A register

Parameters

cpu	z80 CPU object
reg	8-bit register to subtract from A

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