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en:multiasm:piot:chapter_4_3 [2026/01/19 10:53] – [Table] marcinen:multiasm:piot:chapter_4_3 [2026/01/19 15:08] (current) – marcin
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 **R16-R31:**  **R16-R31:** 
 General-purpose registers that can be used with immediate General-purpose registers that can be used with immediate
 +
 +Comparison Table: AVR Registers R0–R15 vs. R16–R31
 +
 +^  Feature                     ^  R0–R15                                                            ^  R16–R31                                        ^
 +|  Instruction compatibility   |  Cannot be used with immediate instructions (LDI, CPI, ORI, ANDI)  |  Fully compatible with immediate instructions   |
 +|  Opcode encoding             |  Not encodable in 4‑bit register fields                            |  Encodable in all immediate‑type formats        |
 +|  Typical compiler usage      |  Less preferred; used for temporary or special roles               |  Preferred for arithmetic and logic operations  |
 +|  Special-purpose roles       |  R0: scratch<br>R1: constant zero                                  |  R26–R31 used as X/Y/Z pointer registers        |
 +|  Pointer support             |  No                                                                |  Yes: X, Y, Z pointers                          |
 +|  Efficiency                  |  Less efficient for immediate operations                           |  More efficient due to shorter opcodes          |
 +|  Multiplication involvement  |  R0/R1 used implicitly for results                                 |  Not used by multipliers                        |
 +|  Suitability in ASM          |  Limited; avoid with immediates; R0/R1 have special rules          |  Recommended for general ALU operations         |
 +|  GCC policy                  |  R1 must remain 0; R0 is volatile                                  |  Treated as normal general-purpose registers    |
  
 <figure avr_registers> <figure avr_registers>
-{{en:multiasm:piot:avr_register1.svg?800|AVR Registers}}+{{en:multiasm:piot:avr_register1.svg?300|AVR Registers}}
 <caption>AVR Registers</caption> <caption>AVR Registers</caption>
 </figure> </figure>
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 <figure avr_registers> <figure avr_registers>
-{{en:multiasm:piot:x_y_z_registers.svg?800|Extended registers}}+{{en:multiasm:piot:x_y_z_registers.svg?400|Extended registers}}
 <caption>Etended Registers</caption> <caption>Etended Registers</caption>
 </figure> </figure>
en/multiasm/piot/chapter_4_3.1768812806.txt.gz · Last modified: by marcin
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