NT6881
Functional Description
1. 6502 CPU
The 6502 is an 8-bit CPU that provides 56 instructions, decimal and binary arithmetic, thirteen addressing modes,
true indexing capability, programmable stack pointer and variable length stack, a wide selection of addressable
memory range, and interrupt input. Other features are also included.
The CPU clock cycle is 3MHz (6MHz system clock divided by 2). Please refer to 6502 data sheet for more
detailed information.
7
7
7
0
0
0
8
Accumulator A
Index Register Y
Index Register X
15
Program Counter PCH
PCL
7
7
0
0
Stack Pointer SP
7
0
N
V
B
D
I
Z
C
Status Register P
Carry
1 = TRUE
Zero
1 = Result ZERO
1 = DISABLE
1 = TRUE
IRQ Disable
Decimal Mode
BRK Command
Overflow
Negative
1 = BRK
1 = TRUE
1 = NEG
Figure 1.1. 6502 CPU Registers and Status Flags
4
ETC [ ETC ]
