 C166 User's Guide | |
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C166 User's Guide
C166 Introduction Compiling Programs Language Extensions
Keywords Memory Models Tiny Model Small Model Medium Model Compact Model Large Model HCompact Model HLarge Model XLarge Model Memory Types near far bdata ebdata idata sdata huge xhuge Memory Type Comparison Pointers with Memory Types Implicit Memory Types Type Qualifiers const volatile Data Types Special Function Registers sfr Types sbit Types bit Types Bit-Addressable Objects Function Declarations Return Values Register Bank Register Mask Interrupt Functions Fast Interrupts Cached Vectors Fast Register Banks Inline Functions Real-Time Function Tasks Inline Assembly Traditional Inline Assembly Extended Inline Assembly Register Use Use in Macro Definitions Preprocessor Advanced Programming Error Messages Library Reference AppendixMemory Type Comparison
When accessing near (bdata, ebdata, idata, and sdata), far, huge, and xhuge variables, the C166 Compiler either generates instructions or calls library routines depending on the device and size of object accessed. Library routines are called when there are no memory type-specific instructions available.
| Memory Type | 80C166 Access | C16x/XC16x Access |
|---|---|---|
| near All Objects | Instructions | Instructions |
| far All Objects | Instructions | Instructions |
| huge All Objects | Library Routines | Instructions |
| xhuge Byte/Word Objects | Library Routines | Instructions |
| xhuge DWord and Larger Objects | Library Routines | Library Routines |
The following examples show the code generated for different memory type accesses on the 80C166 and C16x/XC16x devices. The comparisons show the effects of different memory types on 80C166 and C16x/XC16x instructions and help you estimate the size of the code generated.
near Memory Access
unsigned int j; unsigned int ui; unsigned int near near_uiarray [10]; i = near_array [j];
| 80C166 Code | C16x/XC16x Code |
|---|---|
MOV R4,j SHL R4,#01H MOV R4,[R4+#near_uiarray] MOV ui,R4 |
MOV R4,j SHL R4,#01H MOV R4,[R4+#near_uiarray] MOV ui,R4 |
far Memory Access
unsigned int j; unsigned int ui; unsigned int far far_uiarray [10]; i = far_array [j];
| 80C166 Code | C16x/XC16x Code |
|---|---|
MOV R4,j SHL R4,#01H MOV DPP0,#PAG (far_uiarray) NOP ; pipeline effect MOV R4,[R4+#far_uiarray] MOV ui,R4 |
MOV R4,j SHL R4,#01H EXTP #PAG (far_uiarray),#01H MOV R4,[R4+#POF(far_uiarray)] MOV ui,R4 |
huge Memory Access
unsigned int j; unsigned int ui; unsigned int huge huge_uiarray [10]; i = huge_array [j];
| 80C166 Code | C16x/XC16x Code |
|---|---|
MOV R4,j SHL R4,#01H MOV R2,#SOF (huge_uiarray) MOV R3,#SEG (huge_uiarray) ADD R2,R4 CALLA cc_UC,?C_HLOADI MOV ui,R4 |
MOV R4,j SHL R4,#01H EXTS #SEG (huge_uiarray),#01H MOV R4,[R4+#SOF(huge_uiarray)] MOV ui,R4 |
xhuge Memory Access
Byte/Word Objects
unsigned int j; unsigned int ui; unsigned int xhuge xhuge_uiarray [10]; i = xhuge_array [j];
| 80C166 Code | C16x/XC16x Code |
|---|---|
MOV R4,j MOV R5,#00H ADD R4,R4 ADDC R5,R5 MOV R2,#SOF (xhuge_uiarray) MOV R3,#SEG (xhuge_uiarray) ADD R2,R4 ADDC R3,R5 CALLA cc_UC,?C_HLOADI MOV ui,R4 |
MOV R4,j MOV R5,#00H ADD R4,R4 ADDC R5,R5 MOV R6,R4 MOV R7,R5 MOV R4,#SOF (xhuge_uiarray) MOV R5,#SEG (xhuge_uiarray) ADD R4,R6 ADDC R5,R7 EXTS R5,#01H MOV R4,[R4] MOV ui,R4 |
xhuge Memory Access
DWord and Larger Objects
unsigned int j; unsigned long ul; unsigned long xhuge xhuge_ularray [10]; i = xhuge_larray [j];
| 80C166 Code | C16x/XC16x Code |
|---|---|
MOV R5,#00H ADD R4,R4 ADDC R5,R5 ADD R4,R4 ADDC R5,R5 MOV R2,#SOF (xhuge_ularray) MOV R3,#SEG (xhuge_ularray) ADD R2,R4 ADDC R3,R5 CALLA cc_UC,?C_HLOADL MOV ul,R4 MOV ul+02H,R5 |
MOV R5,#00H ADD R4,R4 ADDC R5,R5 ADD R4,R4 ADDC R5,R5 MOV R2,#SOF (xhuge_ularray) MOV R3,#SEG (xhuge_ularray) ADD R2,R4 ADDC R3,R5 CALLA cc_UC,?C_HLOADL MOV ul,R4 MOV ul+02H,R5 |
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