aLec04_ArchAddrMem - Introduction to Embedded Microcomputer...

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Introduction to Embedded Microcomputer Systems Lecture 4.1 Jonathan W. Valvano Recap Programmer must keep track of format Precision, decimal digits, basis, ASCII Unsigned, signed (2’s complement) Big and little endian Overview Architecture, registers Addressing Modes Memory Allocation Architecture : how pieces are connected together EEPROM I/O $34 Processor RAM $3800 $62 $F004 $B6 $FFFF RegA Bus PTT $0000 $0240 $57 Address Data $F000 PC Figure 2.3. The memory model of a simplified 9S12 computer. To clarify operations that read/write memory, =[U] specifies an 8-bit read from address U
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Introduction to Embedded Microcomputer Systems Lecture 4.2 Jonathan W. Valvano ={U} specifies a 16-bit read from addresses U, U+1 (most significant byte first) [U]= specifies an 8-bit write to address U {U}= specifies a 16-bit write to address addresses U, U+1 (most significant byte first) ldaa #w ;RegA=w ldaa U ;RegA=[U] staa U ;[U]=RegA bra U ;PC=U 6811/6812 I/O port RAM ROM processor Reg A Reg PC The ldaa $3800 instruction reads data from memory 6811/6812 I/O port RAM ROM processor Reg A Reg PC The staa PTT instruction stores CC D X Y SP PC
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aLec04_ArchAddrMem - Introduction to Embedded Microcomputer...

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