DS80C390_00 Datasheet, PDF (114/155 Pages) Dallas Semiconductor – High-Speed Microcontroller User’s Guide Supplement

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DS80C390 High-Speed Microcontroller User’s Guide Supplement
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1
5
(PC_23:16)=((SP))
(SP)=(SP)-1
(PC_15-8)=((SP))
(SP)=(SP)-1
(PC_7:0)=((SP))
(SP)=(SP)-1
22-BIT CONTIGUOUS ADDRESSING MODE
When the AM1 bit is set, the DS80C390 will operate in its 22-bit contiguous addressing mode. This
addressing mode is supported by a full 22-bit Program Counter with eight modified instructions that
operate over the full 22-bit address range. All modified branching instructions will automatically store
and restore the entire contents of the 22-bit Program Counter. The 22-bit DPTR and DPTR1 registers will
function identically to the Program Counter to allow access to the full 22- bit data memory range.
All the DS80C390 instruction opcodes retain binary compatibility to the 8051. Modified instructions are
only different with respect to their cycle/byte/operand count and operate within a contiguous 24-bit
address field. Note that all instructions which utilize the DPTR register now make use of a full 24-bit
register (DPTR=DPX+DPH+DPL and DPTR1=DPX1+DPH1+DPL1). This mode of operation requires
software tools (assembler or compiler) specifically designed to accept the modified length of the new
instructions.
The instructions modified to operate in the 24-bit address mode are summarized in the following table.
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