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CHAPTER 7 SYSTEM REGISTER (SYSREG)
43
7.2 ADDRESS REGISTER (AR)
7.2.1 Address Register Configuration
Figure 7-3 shows the configuration of the address register.
As shown in Figure 7-3, the address register consists of the sixteen bits in address 74H to 77H (AR3 to AR0) of
the system register. However, because the six high-order bits are always set to 0, the address register is actually
10 bits. When the system is reset, all sixteen bits of the address register are reset to 0.
Figure 7-3. Address Register Configuration
74H
Address
77H
75H
76H
AR3
AR2
AR1
AR0
Name
Bit
Symbol
Data
Initial value
when reset
Address register (AR)
(AR)
b
3
b
2
b
1
b
0
0
0
0
0
0
0
0
0
0
0
b
3
b
2
b
1
b
0
b
3
b
2
b
1
b
0
b
3
b
2
b
1
b
0
7.2.2 Address Register Functions
The address register is used to specify an address in program memory when executing an indirect branch
instruction (BR @AR), indirect subroutine call (CALL @AR) or table reference (MOVT DBF, @AR). The address register
can also be put on and taken off the stack by using the stack manipulation instructions (PUSH AR, POP AR).
Items (1) to (4) explain address register operation during execution of each instruction.
The address register can be incremented by using the dedicated increment instruction (INC AR).
(1) Table reference (MOVT DBF, @AR)
When the MOVT DBF, @AR instruction is executed, the data in program memory (16-bit data) located at the
address specified by the value in the address register is read into the data buffer (addresses 0CH to 0FH of
BANK0).
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