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Add read_byte function to return the next byte in memory

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This commit is contained in:
Peter Evans 2017-12-05 20:40:35 -06:00
parent 50a84b4099
commit 89ddd20658
3 changed files with 37 additions and 0 deletions
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1
include/mos6502.h
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@ -112,6 +112,7 @@ extern int mos6502_cycles(mos6502 *, vm_8bit);
extern int mos6502_instruction(vm_8bit);
extern mos6502_instruction_handler mos6502_get_instruction_handler(vm_8bit);
extern void mos6502_execute(mos6502 *, vm_8bit);
extern vm_8bit mos6502_read_byte(mos6502 *);
/*
* Below are some functions that are defined in mos6502.addr.c

15
src/mos6502.c
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@ -352,3 +352,18 @@ mos6502_execute(mos6502 *cpu, vm_8bit opcode)
// Ok -- we're done! This wasn't so hard, was it?
return;
}
/*
* Return the next byte in memory according to the program counter
* register, and then increment the register.
*/
vm_8bit
mos6502_read_byte(mos6502 *cpu)
{
vm_8bit byte;
byte = vm_segment_get(cpu->memory, cpu->PC);
cpu->PC++;
return byte;
}

21
tests/mos6502.c
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@ -128,3 +128,24 @@ Test(mos6502, get_instruction_handler)
cr_assert_eq(mos6502_get_instruction_handler(0x1D), mos6502_handle_ora);
cr_assert_eq(mos6502_get_instruction_handler(0x20), mos6502_handle_jsr);
}
Test(mos6502, execute)
{
START_CPU_TEST(mos6502);
vm_segment_set(cpu->memory, 0, 34);
mos6502_execute(cpu, 0x69);
cr_assert_eq(cpu->A, 34);
END_CPU_TEST(mos6502);
}
Test(mos6502, read_byte)
{
START_CPU_TEST(mos6502);
vm_segment_set(cpu->memory, 0, 0x54);
cr_assert_eq(mos6502_read_byte(cpu), 0x54);
END_CPU_TEST(mos6502);
}