DS80C320-ENG datasheet(65/175 Pages) DALLAS

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High-Speed Microcontroller User’s Guide

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memory space. The location is created using a base address with an index. The base address can be

either the PC or the DPTR. The index is the accumulator. The result is stored in the accumulator. An

example is as follows.

MOVC

A, @A +DPTR

;Load the accumulator with the contents

of program memory

;pointed to by the contents of the DPTR

plus the value in

;the accumulator.

Relative Addressing

Relative Addressing is used to determine a destination address for Conditional branch. Each of these

instructions includes an 8-bit value that contains a two’s complement address offset (–127 to +128) which

is added to the PC to determine the destination address. This destination is branched to when the tested

condition is true. The PC points to the program memory location immediately following the branch

instruction when the offset is added. If the tested condition is not true, the next instruction is performed.

An example is as follows.

$–20

;Branch to the location (PC+2)–20

;if the contents of the accumulator = 0.

Page Addressing

Page Addressing is used by the Branching instructions to specify a destination address within the same

2KB block as the next contiguous instruction. The full 16-bit address is calculated by taking the five

highest order bits for the next instruction (PC+2) and concatenating them with the lowest order 11 bit

field contained in the current instruction. An example is as follows.

0870h

ACALL100h ;Call to the subroutine at address 100h

plus the

;current page address.

In this example, the current page address is 800h, so the destination address is 900h.

Extended Addressing

Extended Addressing is used by the Branching instructions to specify a 16-bit destination address within

the 64KB address space. The destination address is fixed in software as an absolute value. An example

is as follows.

LJMP

0F732h

;Jump to address 0F732h.

DS80C320-ENG Datasheet(PDF) 65 Page - Dallas Semiconductor