1989_MELPS_7700_Software_Manual

Direct Indexed X
Mode
Function
Direct indexed X addressing mode
The contents of the bank-O memory location specified by the result of adding the
second byte of the instruction, the contents of the direct page register and the contents
of the index register X become the actual data. If, however, addition of the
instruction's second byte, the direct page register's contents and the index register
X's contents results in a value that exceeds the bank-O or bank-1 range, the specified
location will be in bank-1 or bank-2.
Instruction:
ADC,
LOY,
AND,
LSR,
ASL,
MPY,
CMP,
ORA,
DEC,
ROL,
DIV,
ROR,
EOR,
SSC,
INC,
STA,
LDA,
STY
LDM,
ex.
: Mnemonic
ADe A,1EH,X
(m=1,x=1)
Machine Code
7516 1 E16
ex.
: Mnemonic
ADe A,1EH,X
(m = 0, x = 1)
Machine Code
75 16 1 E 16
Memory
0000"
Memory
0000"
DATA
Bank-O
1338,.4---------,
A~A+C+
DATAL
I DATAH : DATALI ......{ DATAH
Bank-O
1338,.4------,
c-------
FFFF,.
1------ FFFF,.
Op Code (75,,)
Operand (lE,,)
......
Direct Page
Register
Index
Register X
+11234,.I+~=1338,.
Direct Page Index
Op Code (75,,) Register Register X
Operand (1 E,.) +11234,.1 + ~ = 1338,.
ex.
: Mnemonic
ADe A,1EH,X
(m = 1, x = 0)
Machine Code
75 16 1 E 16
ex.
: Mnemonic
ADe A,1EH,X
(m=O,x=O)
Machine Code
75 16 1E 16
Memory
0000,.
Bank-O
4338,.4-------,
A~A+C+
1 DATAH : DATAL 1- {
Memory
DATAL
DATAH
0000,.
Bank-O
4338,. -ET------,
------
FFFF,.
Direct Page Index
Op Code (75,.) Register Register X
I--_O"-p_er_an_d_(,-l_E,,,,,.)'---I+ 11234,.1 + 1 30E6,.1 = 4338,.
c-------
FFFF,.
Direct Page Index
Op Code (75,.) Register Register X
Operand (1 E,.)
-
+11234,.1+130E6,.1=4338,.
14