I am writing the firmware for an embedded device in C using the Silicon Labs IDE and the SDCC compiler. The device architecture is based on the 8051 family. The function in question is shown below. The function is used to set the ports on my MCU to drive a stepper motor. It gets called in by an interrupt handler. The big switch statement just sets the ports to the proper value for the next motor step. The bottom part of the function looks at an input from a hall effect sensor and a number of steps moved in order to detect if the motor has stalled. The problem is, for some reason the second IF statement that looks like this if (StallDetector > (GapSize + 20))
{
HandleStallEvent();
} always seems to get optimized out. If I try to put a breakpoint at the HandleStallEvent() call the IDE gives me a message saying "No Address Correlation to this line number". I am not really good enough at reading assembly to tell what it is doing but I have pasted a snippet from the asm output below. Any help would be much appreciated.
void OperateStepper(void)
{
//static bit LastHomeMagState = HomeSensor;
static bit LastPosMagState = PosSensor;
if(PulseMotor)
{
if(MoveDirection == 1) // Go clockwise
{
switch(STEPPER_POSITION)
{
case A :
STEPPER_POSITION = B ;
P1 = 0xFD;
break;
case B :
STEPPER_POSITION = C ;
P1 = 0xFF;
break;
case C :
STEPPER_POSITION = D ;
P1 = 0xFE;
break;
case D :
STEPPER_POSITION = A ;
P1 = 0xFC;
break;
default:
STEPPER_POSITION = A ;
P1 = 0xFC;
} //end switch
}
else // Go CounterClockwise
{
switch(STEPPER_POSITION)
{
case A :
STEPPER_POSITION = D ;
P1 = 0xFE;
break;
case B :
STEPPER_POSITION = A ;
P1 = 0xFC;
break;
case C :
STEPPER_POSITION = B ;
P1 = 0xFD;
break;
case D :
STEPPER_POSITION = C ;
P1 = 0xFF;
break;
default:
STEPPER_POSITION = A ;
P1 = 0xFE;
} //end switch
} //end else
MotorSteps++;
StallDetector++;
if(PosSensor != LastPosMagState)
{
StallDetector = 0;
LastPosMagState = PosSensor;
}
else
{
if (PosSensor == ON)
{
if (StallDetector > (MagnetSize + 20))
{
HandleStallEvent();
}
}
else if (PosSensor == OFF)
{
if (StallDetector > (GapSize + 20))
{
HandleStallEvent();
}
}
}
} //end if PulseMotor
}
......以及这一职能下部分的产出......
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:653: if(PosSensor != LastPosMagState)
mov c,_P1_4
jb _OperateStepper_LastPosMagState_1_1,00158$
cpl c
00158$:
jc 00126$
C$MotionControl.c$655$3$7 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:655: StallDetector = 0;
clr a
mov _StallDetector,a
mov (_StallDetector + 1),a
C$MotionControl.c$657$3$7 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:657: LastPosMagState = PosSensor;
mov c,_P1_4
mov _OperateStepper_LastPosMagState_1_1,c
ret
00126$:
C$MotionControl.c$661$2$8 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:661: if (PosSensor == ON)
jb _P1_4,00123$
C$MotionControl.c$663$4$9 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:663: if (StallDetector > (MagnetSize + 20))
mov a,_MagnetSize
mov r2,a
rlc a
subb a,acc
mov r3,a
mov a,#0x14
add a,r2
mov r2,a
clr a
addc a,r3
mov r3,a
clr c
mov a,r2
subb a,_StallDetector
mov a,r3
subb a,(_StallDetector + 1)
jnc 00130$
C$MotionControl.c$665$5$10 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:665: HandleStallEvent();
ljmp _HandleStallEvent
00123$:
C$MotionControl.c$668$2$8 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:668: else if (PosSensor == OFF)
jnb _P1_4,00130$
C$MotionControl.c$670$4$11 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:670: if (StallDetector > (GapSize + 20))
mov a,#0x14
add a,_GapSize
mov r2,a
clr a
addc a,(_GapSize + 1)
mov r3,a
clr c
mov a,r2
subb a,_StallDetector
mov a,r3
subb a,(_StallDetector + 1)
jnc 00130$
C$MotionControl.c$672$5$12 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:672: HandleStallEvent();
C$MotionControl.c$678$2$1 ==.
XG$OperateStepper$0$0 ==.
ljmp _HandleStallEvent
00130$:
ret
看起来像汇编者一样,如果从时间角度讲的话,NOT优化了第二次发言,但如果是这样的话,那么,民主选举学会为什么不允许我在那里打断点呢? 也许这只是一个umb子。