Differences
This shows you the differences between two versions of the page.
| Both sides previous revisionPrevious revisionNext revision | Previous revision | ||
| en:multiasm:papc:chapter_6_10 [2025/10/31 16:19] – [FPU control instructions] ktokarz | en:multiasm:papc:chapter_6_10 [2025/10/31 16:28] (current) – [Table] ktokarz | ||
|---|---|---|---|
| Line 168: | Line 168: | ||
| <table ftrans> | <table ftrans> | ||
| < | < | ||
| - | ^ Mnemonic | + | ^ Mnemonic |
| | **f2xm1** | | **f2xm1** | ||
| | **fyl2x** | | **fyl2x** | ||
| Line 176: | Line 176: | ||
| ===== FPU control instructions ===== | ===== FPU control instructions ===== | ||
| The FPU control instructions help the programmer to save and restore the contents of chosen registers if there is a need to use them in an interrupt handler or inside a function. It is also possible to initialise the state of the FPU unit or clear errors. | The FPU control instructions help the programmer to save and restore the contents of chosen registers if there is a need to use them in an interrupt handler or inside a function. It is also possible to initialise the state of the FPU unit or clear errors. | ||
| - | The **fincstp*** increments and **fdecstp** decrements the FPU register stack pointer. | + | The **fincstp** increments and **fdecstp** decrements the FPU register stack pointer. |
| The following set of instructions can perform error checking while execution (instructions without " | The following set of instructions can perform error checking while execution (instructions without " | ||
| The **finit** and **fninit** initialise the FPU (after checking error conditions or without checking error conditions). | The **finit** and **fninit** initialise the FPU (after checking error conditions or without checking error conditions). | ||
| Line 182: | Line 182: | ||
| The **fstcw** and **fnstcw** store the FPU control word. | The **fstcw** and **fnstcw** store the FPU control word. | ||
| The **fldcw** loads the FPU control word. | The **fldcw** loads the FPU control word. | ||
| - | The **fstenv** and **fnstenr** store the FPU environment. | + | The **fstenv** and **fnstenr** store the FPU environment. The environment consists of the FPU control word, status |
| + | word, tag word, instruction pointer, data pointer, and last opcode register. | ||
| The **fldenv** loads the FPU environment. | The **fldenv** loads the FPU environment. | ||
| - | The **fsave** and **fnsave** save the FPU state. | + | The **fsave** and **fnsave** save the FPU state. The state is the operating environment and full register stack. |
| The **frstor** restores the FPU state. | The **frstor** restores the FPU state. | ||
| - | The **fstsw and **fnstsw** store the FPU status word. There is no instruction for restoring the status word. | + | The **fstsw** and **fnstsw** store the FPU status word. There is no instruction for restoring the status word. |
| The **wait** or **fwait** waits for the FPU to finish the operation. | The **wait** or **fwait** waits for the FPU to finish the operation. | ||
| The **fnop** instruction is the no operation instruction for the FPU. | The **fnop** instruction is the no operation instruction for the FPU. | ||
