IA70C20 Datasheet, PDF (15/27 Pages) InnovASIC, Inc – 8-Bit Microcontroller

IA70C20
8-Bit Microcontroller
3.6 Direct Memory Addressing Mode
Data Sheet
August 19, 2008
The operand for a direct addressing mode instruction is located in memory. The
location is indicated by a 16-bit address. The 16-bit address is preceded by an @
sign and can be written as a constant value or as a label. Figure 6 shows how the
object code produced by an instruction using the direct memory addressing mode
generates a 16-bit effective address.
Figure 6. Direct Memory Addressing Mode Object Code
(PC)
OPCODE
(PC + 1)
(PC + 2)
ADDR MSB
ADDR LSB
16-Bit Effective Address
3.7 Register-File Indirect Addressing Mode
A register pair containing a 16-bit effective address is used in register file indirect
addressing mode. The indirect register file address is written as a register number
(Rn) preceded by an asterisk (*), that is, *Rn. The LSB of the address is
contained in Rn, and the MSB of the address is contained in the previous register
(Rn-1). Figure 7 shows how the object code produced by an instruction using
register file indirect addressing mode generates a 16-bit effective address.
IA211030117-05
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