FreeRTOS/Source/portable/BCC/16BitDOS/common/portasm.h

/*
    FreeRTOS V7.2.0 - Copyright (C) 2012 Real Time Engineers Ltd.
	

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    This file is part of the FreeRTOS distribution.

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*/

#ifndef PORT_ASM_H
#define PORT_ASM_H

typedef void tskTCB;
extern volatile tskTCB * volatile pxCurrentTCB;
extern void vTaskSwitchContext( void );

/*
 * Saves the stack pointer for one task into its TCB, calls
 * vTaskSwitchContext() to update the TCB being used, then restores the stack
 * from the new TCB read to run the task.
 */
void portSWITCH_CONTEXT( void );

/*
 * Load the stack pointer from the TCB of the task which is going to be first
 * to execute.  Then force an IRET so the registers and IP are popped off the
 * stack.
 */
void portFIRST_CONTEXT( void );

/* There are slightly different versions depending on whether you are building
to include debugger information.  If debugger information is used then there
are a couple of extra bytes left of the ISR stack (presumably for use by the
debugger).  The true stack pointer is then stored in the bp register.  We add
2 to the stack pointer to remove the extra bytes before we restore our context. */

#define portSWITCH_CONTEXT()											\
							asm { mov	ax, seg pxCurrentTCB		}	\
							asm { mov	ds, ax						}	\
							asm { les	bx, pxCurrentTCB			}	/* Save the stack pointer into the TCB. */		\
							asm { mov	es:0x2[ bx ], ss			}	\
							asm { mov	es:[ bx ], sp				}	\
							asm { call  far ptr vTaskSwitchContext	}	/* Perform the switch. */						\
							asm { mov	ax, seg pxCurrentTCB		}	/* Restore the stack pointer from the TCB. */	\
							asm { mov	ds, ax						}	\
							asm { les	bx, dword ptr pxCurrentTCB	}	\
							asm { mov	ss, es:[ bx + 2 ]			}	\
							asm { mov	sp, es:[ bx ]				}

#define portFIRST_CONTEXT()												\
							__asm { mov	ax, seg pxCurrentTCB		}	\
							__asm { mov	ds, ax						}	\
							__asm { les	bx, dword ptr pxCurrentTCB	}	\
							__asm { mov	ss, es:[ bx + 2 ]			}	\
							__asm { mov	sp, es:[ bx ]				}	\
							__asm { pop	bp							}	\
							__asm { pop	di							}	\
							__asm { pop	si							}	\
							__asm { pop	ds							}	\
							__asm { pop	es							}	\
							__asm { pop	dx							}	\
							__asm { pop	cx							}	\
							__asm { pop	bx							}	\
							__asm { pop	ax							}	\
							__asm { iret							}


#endif