Jonathan A. Titus

Microcomputer Pioneer

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Lesson 7: Addressing Modes

by David G. Larsen, Peter R. Rony, and Jonathan A. Titus

Internal Registers within the 8080 Chip

IN THIS and several subsequent columns, additional. details will be given concerning the softwarecontrolled operations of an 8080Abased microcomputer. The software instructions, or steps, actually indicate to the microcomputer the tasks it must perform. Just as one might start the day with a list of things to be done and a sequence of performance, the microcomputer, too, must be provided with a sequential list of program steps. This is called software.

In general, we may not be familiar with what each microcomputer instruction does within the microprocessor chip. This does not deter us, however, from using them in all of our programs. Many of us are not familiar with the inner workings of . an internal combustion engine, an automatic transmission, or a Xerox machine; our lack of knowledge does not prevent us from using them daily.
Read More: Adobe Acrobat PDF FileInternal Registers.pdf [311KB]

Register Pair Instructions
IN THE NOVEMBER column we discussed the single-byte data transfer instructions MOV D, S and MVI >82< in the 8080 microprocessor instruction set. We summarize the significant point of the column in Figure 1, which indicates that for MVI r >82< instruction, the data byte transferred to a register comes from the instruction itself, whereas for the MOV D S instruction, the data byte is copied into the destination register D from the source register S.
Read More: Adobe Acrobat PDF FileRegister Pair Instructions.pdf [1.19MB]