SDA55XX Datasheet, PDF (64/230 Pages) Infineon Technologies AG – Preliminary & Confidential

SDA 55xx
Preliminary & Confidential
Immediate Addressing
Program Memory
Microcontroller
Base Register plus Index-Register Indirect Addressing
Program Memory (@DPTR + A, @PC + A)
6.1.3.1 Register Addressing
Register addressing accesses the eight working registers (R0 … R7) of the selected
register bank. The PSW register flags RS1 and RS0 determine which register bank is
enabled. The least significant three bits of the instruction opcode indicate which register
is to be used. ACC, B, DPTR and CY, the Boolean processor accumulator, can also be
addressed as registers.
6.1.3.2 Direct Addressing
Direct byte addressing specifies an on-chip RAM location (only low part) or a special
function register. Direct addressing is the only method of accessing the special function
registers. An additional byte is appended to the instruction opcode to provide the
memory location address. The highest-order bit of this byte selects one of two groups of
addresses: values between 00_H … 7F_H access internal RAM locations, while values
between 80_H … 0FF_H access one of the special function registers.
6.1.3.3 Register-indirect Addressing
Register-indirect addressing uses the contents of either R0 or R1 (in the selected
register bank) as a pointer to locations in the 256 bytes of internal RAM. Note that the
special function registers are not accessible by this method.
Execution of PUSH and POP instructions also use register-indirect addressing. The
stack pointer may reside anywhere in internal RAM.
6.1.3.4 Immediate Addressing
Immediate addressing allows constants to be part of the opcode instruction in program
memory.
An additional byte is appended to the instruction to hold the source variable. In the
assembly language and instruction set, a number sign (#) precedes the value to be used,
which may refer to a constant, an expression, or a symbolic name.
6.1.3.5 Base Register plus Index Register-indirect Addressing
Base register plus index register-indirect addressing allows a byte to be accessed from
program memory via an indirect move from the location whose address is the sum of a
Semiconductor Group
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User’s Manual July 99