Oki ML63326, User Manual, Page: 42 / 322

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ML63326 User's Manual
Chapter 2 CPU and Memory Spaces
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2.2.4 Current Bank Register (CBR), Extra Bank Register (EBR), HL Register (HL), XY
Register (XY)
The CBR, EBR, HL, and XY registers are used for indirect addressing of data memory.
The CBR and EBR registers indicate the data memory bank. The HL and XY registers indicate
addresses in the bank. CBR is also used in combination with 8-bit data in the instruction code
for direct addressing within the current bank.
Figure 2-1 shows the various register combinations.
CBR
CBR
EBR
EBR
CBR
H L
X Y
H L
X Y
Instruction code 8-bit data
+
+
+
+
A11–A8 A7–A4 A3–A0
+
Figure 2-1 Various Register Combinations
A11 to A0 in Figure 2-1 indicate data memory addresses (4K nibbles max.).
At system reset, the CBR, EBR, HL, and XY registers are initialized to "0".
When an interrupt occurs, a "PUSH HL" or "PUSH XY" instruction can be used if necessary
to save the CBR, EBR, HL, and XY registers on the register stack. These registers can be
restored with a "POP HL" or "POP XY" instruction.
The CBR, EBR, HL, and XY registers are assigned to special function register (SFR)
addresses 0F9H to 0FEH.
e
3
e
2
e
1
e
0
EBR
bit 3 bit 2 bit 1 bit 0
c
3
c
2
c
1
c
0
CBR
bit 3 bit 2 bit 1 bit 0
H
bit 3 bit 2 bit 1 bit 0
L
bit 3 bit 2 bit 1 bit 0
h
3
h
2
h
1
h
0
l
3
l
2
l
1
l
0
X
bit 3 bit 2 bit 1 bit 0
Y
bit 3 bit 2 bit 1 bit 0
x
3
x
2
x
1
x
0
y
3
y
2
y
1
y
0
(0FDH)
(R/W)
(0FCH)
(R/W)
(0FBH)
(R/W)
(0FAH)
(R/W)
(0F9H)
(R/W)
(0FEH)
(R/W)