ADE5166_08 AD [Analog Devices], ADE5166_08 Datasheet - Page 79

• Manufacturer Part Number: ADE5166_08
• Description: Single-Phase Energy Measurement IC with 8052 MCU, RTC, and LCD Driver
• Manufacturer: AD [Analog Devices]

Table 66. 8052 Addressing Modes
Addressing Mode
Immediate
Direct
Indirect
Extended Direct
Extended Indirect
Code Indirect
Immediate Addressing
In immediate addressing, the expression entered after the number
sign (#) is evaluated by the assembler and stored in the memory
address specified. This number is referred to as a literal because
it refers only to a value and not to a memory location. Instructions
using this addressing mode are slower than those between two
registers because the literal must be stored and fetched from
memory. The expression can be entered as a symbolic variable
or an arithmetic expression; the value is computed by the
assembler.
Direct Addressing
With direct addressing, the value at the source address is moved
to the destination address. Direct addressing provides the fastest
execution time of all the addressing modes when an instruction
is performed between registers using direct addressing. Note that
indirect or direct addressing modes can be used to access general-
purpose RAM Address 0x00 through Address 0x7F. An instruction
with direct addressing that uses an address between 0x80 and
0xFF is referring to a special function memory location.
Indirect Addressing
With indirect addressing, the value pointed to by the register is
moved to the destination address. For example, to move the
contents of internal RAM Address 0x82 to the accumulator, use
the following two instructions, which require a total of four
clock cycles and three bytes of storage in the program memory:
MOV
MOV
Indirect addressing allows addresses to be computed and is
useful for indexing into data arrays stored in RAM.
Note that an instruction that refers to Address 0x00 through
Address 0x7F is referring to internal RAM, and indirect or direct
addressing modes can be used. An instruction with indirect
addressing that uses an address between 0x80 and 0xFF is
referring to internal RAM, not to an SFR.
R0,#82h
A,@R0
Example
MOV A, #A8h
MOV DPTR, #A8h
MOV A, A8h
MOV A, IE
MOV A, R0
MOV A, @R0
MOVX A, @DPTR
MOVX A, @R0
MOVC A, @A+DPTR
MOVC A, @A+PC
JMP @A+DPTR
Bytes
2
3
2
2
1
1
1
1
1
1
1
Core Clock
Cycles
2
3
2
2
1
2
4
4
4
4
3
Rev. 0 | Page 79 of 148
Extended Direct Addressing
The DPTR register is used to access internal extended RAM in
extended indirect addressing mode. The ADE5166/ADE5169
provide 2 kB of internal extended RAM (XRAM), accessed
through MOVX instructions. External memory spaces are not
supported on the ADE5166/ADE5169.
In extended direct addressing mode, the DPTR register points
to the address of the byte of extended RAM. The following code
moves the contents of extended RAM Address 0x100 to the
accumulator:
MOV
MOVX
These two instructions require a total of seven clock cycles and
four bytes of storage in the program memory.
Extended Indirect Addressing
The internal extended RAM is accessed through a pointer to the
address in indirect addressing mode. The ADE5166/ADE5169
provide 2 kB of internal extended RAM, accessed through MOVX
instructions. External memory is not supported on the ADE5166/
ADE5169.
In extended indirect addressing mode, a register holds the
address of the byte of extended RAM. The following code
moves the contents of extended RAM Address 0x80 to the
accumulator:
MOV
MOVX
These two instructions require six clock cycles and three bytes
of storage.
Note that there are 2 kB of extended RAM, so both extended
direct and extended indirect addressing can cover the whole
address range. There is a storage and speed advantage to using
extended indirect addressing because the additional byte of
addressing available through the DPTR register that is not
needed is not stored.
From the three examples demonstrating the access of internal
RAM from 0x80 through 0xFF and extended internal RAM
from 0x00 through 0xFF, it can be seen that it is most efficient
to use the entire internal RAM accessible through indirect
access before moving to extended RAM.
Code Indirect Addressing
The internal code memory can be accessed indirectly. This can be
useful for implementing lookup tables and other arrays of constants
that are stored in flash memory. For example, to move the data
stored in flash memory at Address 0x8002 into the accumulator,
MOV
CLR
MOVX
The accumulator can be used as a variable index into the array
of flash memory located at DPTR.
DPTR,#100h
A,@DPTR
R0, #80h
A, @R0
DPTR,#8002h
A
A,@A+DPTR
ADE5166/ADE5169