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1、 EM78P156EL 间接寻址的应用间接寻址的应用 义隆电子股份有限公司义隆电子股份有限公司 第一版第一版 2008年年11月月 Trademark Acknowledgments: IBM is a registered trademark and PS/2 is a trademark of IBM. Windows is a trademark of Microsoft Corporation. ELAN and ELAN logo are trademarks of ELAN Microelectronics Corporation. Copyright 2008 by ELAN M
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9、23, Zone 115, Lane 572, Bibo Rd. Zhangjiang Hi-Tech Park Shanghai, CHINA 201203 Tel: +86 21 5080-3866 Fax: +86 21 5080-4600 EM78P156EL 间接寻址的应用间接寻址的应用 EM78P156EL的应用笔记的应用笔记 1 目目 录录 一、 相关寄存器 .2 1、 R0(间接地址寄存器)2 2、 R4(RSR)RAM 选择寄存器2 二、 使用步骤.2 三、 范例.2 EM78P156EL 间接寻址的应用间接寻址的应用 2 EM78P156EL的应用笔记的应用笔记 EM78P
10、156EL 间接寻址的应用间接寻址的应用 一、 相关寄存器一、 相关寄存器 1、 R0(间接地址寄存器间接地址寄存器) R0 并非一个实际工作的寄存器，而只作为间接寻址用。任何对 R0 进行操作的指令，实际上是存取由 RAM 选择寄存器 R4 所指定的 RAM内容。 2、 R4(RAM 选择寄存器选择寄存器) R4 寄存器各位定义如下： Bit 7 Bit 6：未用 。 Bit 5 Bit 0：在间接寻址方式中用于选择寄存器（地址: 00 3F)。 R4 在间接寻址时作为 RAM选择寄存器使用。注意：任何对 R0 进行操作的指令,实际上是存取由 R4 所指定的 RAM的内容。在间接寻址模式里，
11、R4 的 05位用来选择寄存器，其地址从 003FH。 二、 使用步骤二、 使用步骤 1. 设置间接寄存器R4的初始值； 2. 对寄存器R0进行操作。 如： MOV A, 0X20 ;设定A寄存器的值为0X20 MOV 0X04, A ;设定间接寻址寄存器(0X04)的内含值0X20 MOV A, 0X35 ;设定A寄存器的值为0X35 MOV R0, A ;将A的值送到指定的RAM地址中(RAM地址 ;0X20=0X35) 以上指令的执行结果为: 寄存器地址0X20内的值变为0X35 三、 范例三、 范例 ;* ;下面的范例实现对0X100X3F的RAM清零 ;* EM78P156EL 间接
12、寻址的应用间接寻址的应用 EM78P156EL的应用笔记的应用笔记 3 ;MCU：EM78P156EL ;Oscillator：Crystal 3.58MHz ;Clock： 2 ;WDT： Disable ;编译软件：WicePulse version 2.6081015 INCLUDE “EM78P156EL.INC“ ORG 0X00 JMP INITIAL ORG 0X50 INITIAL: MOV A, 0X10 MOV RSR, A ;RSR指至RAM中0X10的地址 MAIN: CLR R0 ;清除RSR指定地址的内容 INC RSR ;RSR指到下一个地址 MOV A,RSR AND A,0X3F JBS Z ;判断是否0x100x3F已清除 JMP MAIN JMP $
