NT6881
3. Mask ROM: 6K X 8 bits
The built-in mask ROM program code, executed by the 6502 CPU, has a capacity of 6K X 8-bit and is addressed from
E800H to FFFFH.
4. SRAM: 256 X 8 bits
The built-in SRAM is used for general purpose data memory and for stack area. SRAM is addressed from 0080H to
017FH. Because the 6502 default stack pointer is 01FFH, the stack area will map $01FF-$0180 to $00FF-$0080, thus the
programmer can set “ S” register to 7FH when starting program, allowing stack point is 017FH.
as;
LDX
TXS
#$7F
$0000
$001F
System Registers
Unused
$0080
$00FF
RAM
$0100
$017F
RAM
stack pointer
Unused
$E800
$FFFA
ROM
NMI Vector
NMI-L
NMI-H
RST-L
RST-H
IRQ-L
IRQ-H
$FFFB
$FFFC
$FFFD
RESET Vector
IRQ Vector
$FFFE
$FFFF
7
ETC [ ETC ]
