Freescale Semiconductor DRM079 User's Manual
Contents
1. Voo ON CHIP R Vpop COMPARATOR ie E 7k5 C TEMP SENSOR 22nF 10k MCU BOUNDARY ele hd Figure 3 3 Emulated ADC Schematic The schematic of the emulated ADC in this application is shown in Figure 3 3 The ADC input is the temperature sensor resistor ladder When the comparator is not measuring the capacitor C is fully discharged where the positive terminal of the comparator is pulling low When the temperature sensor measurement is required the comparator is then enabled and the terminal turns to analog input voltage across C starts to ramp up The 8 bit internal modulo timer is used to monitor the time taken for the RC to charge to a level that matches the voltage across the temperature sensor The timer counter value is captured and used as the basis for the emulated ADC conversion With a 10kQ temperature sensor and 7 5kQ pullup resistor the ADC absolute dynamic range is from OV to about 0 57 x Vpp i e about 2 85V Timer clock is chosen to be eight times slower than the bus clock the timer resolution becomes 2us The RC charging profile follows EQ 3 1 Given the RC constant is 4K7Q x 22nF the timer counter value against the temperature sensor reading with 5V Vpp is shown in Table 3 2 t V Vol e EQ 3 1 Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 18 Freescale Semiconductor Table 3 2 RC Charging Profile Temperature Sensor Measurement Against Timer Count2. Time us Voltage across the ADC Readout Temperature Sensor V Timer Count 0 0 0 2 0 10 1 4 0 19 2 6 0 28 3 and so on 86 2 82 43 88 2 87 44 90 2 91 45 and so on 126 3 52 63 Table 3 2 shows the entire dynamic range of the temperature sensor voltage can be covered by about 44 timer counts For convenience the timer overflow period is set to 63 which is identical to the size of the paging window 00C0 to 00FF in the MC9RS08KA2 The timer value captured can be used directly as an index to the paging window for the target PWM period value lookup The code below shows how the timer value is captured using RS08 instructions ReadSensor mov mov mov mov bset wait brclr mov bset ely wait mov rts NoReading mov clr mov rts 63 m m AC AC MTI AC AC TIM _BUS_CLK MTIM_DIV_8 MTIMMOD MTIMSC_TRST mMTIMSC_TOIE MT ACMPSC_ACME mACMPSC_ACIE ACMP L PSC_ACF ACMPSC p PSC_ACF ACMPSC NoReading CNT SensorReading PSC_ACF ACMPSC PSC i T TIMSC_TSTP mMTIMSC_TRST MT TIM_BUS_CLK MTIM_DIV_256 MT 0 SensorReading PSC MTIMSC_TSTP mMTIMSC_TRST M TIM_BUS_CLK MTIM_DIV_256 MT Variable Speed DC Fan Control using TIMSC MTIMCLK Change Timer resolution OF period IMSC Reset and Start Timer _OUTPUT_RAISING ACMPSC Enable ACMP start RC rise Clear ACMP Flag Capture
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4. beq WaitAgain if same Fan speed reach target then exit DecPeriod 1f bigger decrement DeadTim lda DeadTime cmp MinDeadTime blo WaitAgain dec DeadTime bra WaitAgain IncPeriod 1f smaller increment DeadTim lda DeadTime cmp MaxDeadTime bhs WaitAgain inc DeadTime bra WaitAgain WaitAgain 8 Bump COP sta MAP_ADDR_6 SRS Bump COP wait mov mMMTIMSC_TSTP mMTIMSC_TRST MTIMSC mask interrupt and clear flag 9 Repeat the control cycle bra FanControlLoop ESSE SSS SSS SS SSS SSS SEEEEEEEEEEEEEEEEEEEEE EEE SESS SS SESS SESEEEEEEEEEEEEEEEEEESESESS Delay 16ms ESSE SS SSS SSS SSS III ESSE SSS SESE SSESEEEEEEEEEEEEEEEEEESESSES Delay mov 255 MTIMMOD OF period mov mMMTIMSC_TRST mMTIMSC_TOIE MIIMSC Reset and Start Timer wait mov mMMTIMSC_TSTP mMTIMSC_TRST MTIMSC mask interrupt and clear flag sta MAP_ADDR_6 SRS Bump COP rts 2292992292 O 0 O O OD O O O O O O O D O O D D 0 D D 0 00 0 0 9 0 0 O O 0 O 0 0p 0 O 0 o 9 9 Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 Freescale Semiconductor 29 Implementation L SetPWM Mov 255 MTIMMOD OF period mov MMTIMSC_TRST mMTIMSC_TOIE MIIMSC Reset and Start Timer lda 20 mov mKBISC_KBIE KBISC Enable Interrupt amp Edge only bset KBISC_KBACK KBISC Clear Flag stx PTAD Drive coil TimingLoop belr TIMSC_TOF MTIMSC Clear TOF wait brset KBISC_KBF KBISC HallFound HALL sensor edge found dbnza
5. energized As the magnetic field switches to the next motor position or pole the inertia of the rotor keeps the motor running As a result two commutation steps moves the rotor by 180 degrees or one motor phase One mechanical revolution is contributed by four commutation steps To avoid conflict to the magnetic field adjacent coils cannot be energized at the same time Dead time where all coils are un energized must be added between each commutation step Figure 2 1 Bi phase BLDC Motor Schematic 2 2 Rotor Position Control The key idea to prevent a motor lockup concerns rotor position detection The time to switch the commutation is critical Energizing coil pair for too long will kill the rotor inertia and the motor stops running This is called motor lockup Switching the commutation too soon will lose control to the rotor and eventually stall the motor The rotor position in this design is determined by a hall sensor which will respond to the change in magnetic field Hall sensor output toggles when the magnetic field changes its polarity Positioning the hall sensor between the coils at 45 degree to the stator coils as shown in Figure 2 1 can effectively detect the rotor position In this case the hall sensor output toggles when the rotor magnets is aligned to the coils Commutation should switch at this time from one coil pair to the next coil pair Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 Freescale Semiconduc
6. an 8 bit modulo timer keyboard interrupt and analog comparator The device is available in small 6 and 8 pin packages Features of the MC9RS08KA2 include 8 bit RS08 core Up to 10 MHz bus frequency at 1 8V for 100 ns minimum instruction time RSO0O8 instruction set Supports tiny short address mode 14 byte fast access RAM Allows emulation of HC08 HCS08 zero offset index addressing mode instructions Third generation Flash and RAM extremely fast byte writable programming 63 Byte RAM 2K Byte Flash Flexible clock options e 4 Bidirectional I O lines with software selectable pull up eliminates need for external resistors Analog comparator e Real time interrupt e 8 bit timer with 8 bit prescale System protection Resets in instance of runaways or corrupted code Low voltage detection Illegal opcode and illegal address detection Flash security feature Single wire debugging and emulation interface eliminates need for expensive emulation tools or development hardware 1 3 DC Fan Reference Design Targets Table 1 1 Design Targets Item Requirement Motor Type Bi phase BLDC motor Fan Dimensions 60mm x 60mm x 25mm Operating Voltage 12V Current Rating 0 18A max Speed 1000 to 4000 RPM Temperature Feedback Yes Fault Detection Air flow blocking motor jam Fault Notification Buzzer alarm Variable Speed DC Fan Control using the MC9RSO8KA2 Rev
7. range are also defined and shown in Table 3 3 EQ 3 2 shows how the target PWM period value is calculated The target value is compared with the measured PWM period every 180 degrees of rotation The ADC readout delay is considered as constant therefore it is omitted from the motor speed measurement and should be deducted from the target period calculation too ADCDelay TargetPWMPeriod EQ 3 2 TimerResolution The timer resolution used in the application is 64s the ADC readout time contributes a constant delay to the overall PWM period which is 128us in this application The target PWM period used for motor speed control is shown in Table 3 3 The table is stored in the upper memory FLASH In RS08 architecture upper memory access is done through the paging window address 00C0 to 00FF where the PAGESEL register is defining the page to be accessed Simple table lookup method which uses the captured timer value from the temperature sensor readout as an index in the paging window for the target PWM period conversion For software implementation the target motor speed must be deduced in terms of timer counts where it is used as the target PWM period per commutation By using Table 3 2 and Table 3 3 a look up table can be constructed where the ADC readout value is used as an index to retrieve the target PWM period for a specific temperature range Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 20 Freescale
8. timer count Clear ACMP Flag disable ACMP delay to OF and make the read process deterministic IMSC mask interrupt and clear flag IMCLK Reset Timer resolution Smallest Number disable ACMP mask interrupt and clear flag IMCLK Reset Timer resolution the MC9RS08KA2 Rev 0 Freescale Semiconductor 19 Implementation As described in the previous section the overall dead time duration should be deterministic the double WAIT statements in the subroutine can ensure the execution time to be mostly constant When the MCU is woken up from the first WAIT which is normally triggered by the comparator the timer counter value is captured and the MCU is then returned to WAIT mode until the timer is overflowed The subroutine execution time would be equivalent to the timer overflow period 128us plus some software overhead 3 4 1 Temperature Conversion In general the channel resistance of the temperature sensor reduces as the temperature increases The corresponding channel resistance against temperature can usually be retrieved from the sensor data sheet For this application the operating temperature range is defined from 25 C to 100 C When the ambient temperature is 100 C or above the motor is at maximum speed The speed drops as the temperature decreases in 5 C steps Given the sensor channel resistance values the voltage across the sensor can be calculated The corresponding motor speed for a specific temperature
9. which is defined by the time that the coils are energized until the Hall sensor is toggled The Hall sensor output indicates the position of the rotor and defines the time to switch to the next commutation step In this design the motor speed or the PWM period is continuously monitored It is a closed loop control design If the motor speed is faster PWM period is shorter than the target value the dead time duration is extended until the target PWM period is reached Similarly when the motor speed is slower than the target value the dead time duration is shortened The rotor starts off at the slowest speed Shortening the dead time causes the coils to energize earlier and the rotor is pushed pulled to the next pole position sooner causing motor speed to increase Similarly when the dead time is extended the rotor hangs loose for a longer time before it is pushed pulled to the next pole position As a result the motor speed decreases The target motor speed against temperature is predefined It is updated periodically based on the information from the temperature sensor Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 12 Freescale Semiconductor Motor Startup Dramatic changes in the dead time value will cause the motor to stall In this design a software loop in the MCU will control the dead time variation Even with the dramatic change in the temperature sensor reading the software loop will only allow the dead time to chan
10. 0 8 Freescale Semiconductor Bi Phase BLDC Motor 1 4 Bi Phase BLDC Motor The brushless DC motor BLDC design for DC fan is commonly consist of a permanent magnet attached on the rotor and the stator phase coil windings are mounted on the motor shaft as illustrated in Figure 1 2 The BLDC has no brushes on the rotor and the commutation is performed electronically at certain rotor positions Axle f Permanen y Magnets Figure 1 2 Bi Phase BLDC Motor Diagram Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 Freescale Semiconductor Introduction Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 10 Freescale Semiconductor Commutation Chapter 2 Motor Control 2 1 Commutation The typical bi phase BLDC has one pole pair per phase Each commutation rotates the rotor by 90 degrees and four commutation steps complete a mechanical revolution Each pole pair is implemented by two coils with four coils in total for a bi phase motor Energizing a pair of coils either coil A amp C or coil B amp D as shown in Figure 2 1 induces magnetic fields that push the equal polarity rotor magnets away from the energized coils and at the same time the opposite polarity rotor magnets are pulled toward the coils Rotation starts and this is called a commutation step When the rotor magnetic pole is aligned with the energized coils the coils are deactivated and the previously un energized pair of coils are then
11. 3 A VEEN 255045545 0 69 1045 II EENE Et 3 IO 2 4 e A i A na 2 doi alla E ap aa let ea dat dp i cl a at 0 e seats 2 5 a St sayas ie 8 a ae d oieri n e Azi de pha aphaca a QS ahus E T 2 6 PGH SISCAR e l m alto at SA a Chapter 3 Implementation 3 1 a ce s scie va d no aa d i dn n d da en i n ad n a n nl i e d ee 3 2 Hardware Resources occ oe eke aaa ie i n a dt aa e a 3 3 Oe LOGE i e ca e ea ac e el a e e e a le 605 49 a ac e d NAAA 3 4 Temperature Sensor Measurement ceea 3 4 1 Temperature Conversion aaa a e AAA AAA AA REA Appendix A Schematic Appendix B Program Listing Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 Freescale Semiconductor Table of Contents Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 6 Freescale Semiconductor Chapter 1 Introduction 1 1 Introduction This document describes the implementation of a DC brushless fan controller using the Freescale ultra low cost MC9RS08KA2 8 bit microcontroller MCU The design contains a temperature sensor the MCU reads with control on fan speed against the ambient temperature Complete coding and schematic are included VARIABLE RESISTOR TO EMULATE A TEMPERATURE SENSOR MC9RS08KA2 MCU IN 8 PINNARROW BODY SOIC PACKAGE BUZZER Figure 1 1 The MC9RS08KA2 DC Fan Reference Design The DC fan used is a brushless DC motor fan It is widely used in chip cooling or system ventilation applications In the market most of th
12. Ambient temperature reading is taken from a temperature sensor which is equivalent to a diode Temperature variation alters the diode channel current as well as the effective channel resistance The temperature sensor is combined with a 7 5kQ resistor in a potential divider arrangement The built in analog comparator is used to compare the temperature sensor ladder voltage with an defined RC network to deduce the absolute temperature As described in the previous section the motor speed is controlled by varying the absolute dead time This is updated every 128ms in the application As in all RS08 S08 devices the MC9RSO8KA2 MCU has a programmable real time interrupt RTI feature In this case it is used to notify the MCU to refresh the target PWM period every 128ms 3 3 Control Loop Figure 3 2 shows the firmware control loop flow chart The KBI or Hall sensor output is continuously monitored for trigger signals within a defined time A motor fault condition occurs when there are no trigger signal and the firmware goes into a forever loop Commutation is stopped and the buzzer is alarmed The target PWM period based on the temperature sensor reading is updated every 128ms And on each 180 degrees rotation of the rotor two commutation steps the actual PWM period is compared with the target PWM period If they are different the absolute dead time will be altered and the actual PWM period will gradually change towards the target PWM period On
13. Center P O Box 5405 Denver Colorado 80217 1 800 441 2447 or 303 675 2140 Fax 303 675 2150 LDCForFreescaleSemiconductor hibbertgroup com DRMO79 Rev 0 5 2006 RoHS compliant and or Pb free versions of Freescale products have the functionality and electrical characteristics of their non RoHS compliant and or non Pb free counterparts For further information see http www freescale com or contact your Freescale sales representative For information on Freescale s Environmental Products program go to http www freescale com epp Information in this document is provided solely to enable system and software implementers to use Freescale Semiconductor products There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document Freescale Semiconductor reserves the right to make changes without further notice to any products herein Freescale Semiconductor makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does Freescale Semiconductor assume any liability arising out ofthe application or use of any product or circuit and specifically disclaims any and all liability including without limitation consequential or incidental damages Typical parameters that may be provided in Freescale Semiconductor data sheets and or specifications can and do vary in
14. KA2 Rev 0 Freescale Semiconductor 31 Implementation 255 lda Quiet Clear buzzer 7 PTAD MT IMMOD BUZZER 30 belr mov mov Reset and Start Timer mMTIMSC_TOIE MTIMSC mMTIMSC_TRST wait mov mask interrupt and clear flag Bump COP MTIMSC mMTIMSC_TRST SRS mMTIMSC_TSTP r MAP_ADDR_6 Quiet sta dbnza SoundBuzzer bra s o oe oe oe o oe oe o oe ao ao s o o o o o oe oe oe o o o s oe oe oe o oe oe oe oe oe oe oe o o o o o oe oe oe oe oe o o oe oe o o oe oe o o o o o s Lookup Table r s o oe oe oe oe oe ao o o s s s o o o o o o o oe o o o oe oe oe oe oe oe oe oe o o oa o o oa o9 o o o o s s s ep o a oe oe oe oe oe o o oe oe oo s TableStart org 57 57 57 57 60 63 67 71 76 82 82 88 88 96 96 105 105 115 115 115 128 128 128 128 144 144 144 144 165 165 165 Diy b b b b de de r657 19371937193 1931932325 2324 2322392 2522392 232 232723257 232 2325 2327 2322327 232 23827 232 232 23925 23927 23272325 292 2327 23527232 dc dc oe o oe oe oe oe oe ao s s s s s o o o o oe o o oe o o o s o o9 o o o o o o o o o o o s o o oa o o oe oe oe oe oe oe o o oe oe oe o o s
15. MSC mask interrupt and clear flag mov MIIM_BUS_CLK MTIM_DIV_256 MTIMCLK Reset Timer resolution rts EGG SSS SESS EEEEECEEEEEEEEEEEEEEEE ESSE SSS SSS SESSEEEEEEEEEEEEEEEEESESSESES 6 bit Table Lookup ESSE SSS SSS SS SSS SSS SESEEEEEEEEEEEEEEEEEEEE EES SESS SESS SESESEEEEEEEEEEEEEEEEESEESSES TableLookup bset SRTISC_RTIACK MAP_ADDR_6 SRTISC 5 mov HIGH_6_13 TableStart PAGESEL 5 Calculate the PAGE lda SensorReading 73 add ScO 2 Reference to paging window tax PZ lda y X 73 sta TargetPeriod 72 mov HIGH_6_13 SOPT PAGESEL Hes rts 3 Error Handling Stop the motor Sound the buzzer about 520Hz MotorHang eur PTAD Clear PWMp and PWMn lda MotorRunning Check software flag bne SoundBuzzer 1 Motor is running jmp ResetPosition SoundBuzzer mov mMMTIMSC_TSTP mMTIMSC_TRST MTIMSC mask interrupt and clear flag clr KBISC mask KBI lda 255 sta MAP_ADDR_6 SRS Bump COP Beep a 20 duty cycle loop bset BUZZER PTAD Drive buzzer mov 6 MTIMMOD mov MMTIMSC_TRST mMTIMSC_TOIE MTIMSC Reset and Start Timer wait mov mMMTIMSC_TSTP mMTIMSC_TRST MTIMSC mask interrupt and clear flag sta MAP_ADDR_6 SRS Bump COP Perr BUZZER PTAD Clear buzzer mov 24 MTIMMOD mov mMMTIMSC_TRST mMTIMSC_TOIE MTIMSC Reset and Start Timer wait mov mMMTIMSC_TSTP mMTIMSC_TRST MTIMSC mask interrupt and clear flag sta MAP_ADDR_6 SRS Bump COP dbnza Beep Variable Speed DC Fan Control using the MC9RSO8
16. O AS Asz aznz ED HOLOENNOD NYA DATE oy 14 Y ASZ aznz 99 TIWH TIVH UND UND zi a TI PI O WOD mlaja AZT Asz aznz E TE ZSWAZ a Y AZT UND Tu NI AI T O AZI Td 23 Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 Freescale Semiconductor Implementation Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 24 Freescale Semiconductor Appendix B Program Listing Temperature Sensor Measurement NA NOA PA OR Rue wanay e O O RO KI RR c copyright Freescale Semiconductor 2006 ALL RIGHTS RESERVED BR ROR DS a a a A dia At A EEREN KREAKE EEEE RARER KIER AE IE RERE Aaa a a END Sa aS Ma gh aL aN Pa elie IS SOR Dy el RC LA ue taqta Suara e head S le TES Ra aT DC Fan Coding for 9RSO8KA2 Author Date PTA4 KBI4 PTAS KBI5 A A A A F A HF SE H XDEF include Vincent Ko Jan 2006 PTAO KBIO ACMP PTA1 KBI1 ACMP PTA2 KBI2 TCLK RESETb VPP PTA3 ACMPO BKGD MS Entry MCORSO8KA2 inc RC input Temp Hall sensor input input Buzzer PWM PWM nclude derivative specific macros KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK AS L ICS Definition r TGS DIA equ 00 ICS_DIV_2
17. PWM output 1 VOLTAGE 12 REGULATION VDD gt HALL gt Pw PTAS BUZZER BI PHASE MOTOR L lt PTA4 U eel Rc ACMP TEMP SENSOR gt PTA5 MC9RS08KA2 Figure 3 1 DC Fan Design Block Diagram 3 2 Hardware Resources In this application the low cost MC RS08KA2 MCU is used The device has a built in 8 bit modulo timer which is used to control the timing for the PWM drive Bus frequency is chosen to be 4MHz The design target for the maximum motor speed is 4000 rpm the timer must have enough resolution to measure the shortest PWM period that is less the 3 75ms per commutation step Timer prescalar is selected as 256 and the timer resolution becomes 64us Table 3 1 Hardware Configuration Bus Frequency 4MHz Timer Clock for motor speed monitoring 4MHz 256 16kHz Timer Resolution 64us Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 Freescale Semiconductor 15 Implementation Hall sensor output is connected to the MCU s GPIO port PTA2 which has a programmable edge trigger keyboard interrupt KBI The programmable edge trigger feature provides an effective way to monitor the Hall sensor signal As mentioned in the previous section the direction of rotation can be detected by the polarity of the Hall sensor output edge Monitoring the signal edge is achieved by altering the KBI edge trigger polarity for each commutation step
18. Semiconductor Temperature Sensor Measurement Table 3 3 Temperature Conversion Table Temperature lies stance sa ne pl d Target PWM Period Co from sensor data sheet ee rpm Timer Counts 25 or below 10 2 86 1000 232 30 34 8 082 2 59 1200 193 35 39 6 577 2 34 1400 165 40 44 5 387 2 09 1600 144 45 49 4 441 1 86 1800 128 50 54 3 683 1 65 2000 115 55 59 3 024 1 44 2200 105 60 64 2 53 1 26 2400 96 65 69 2 128 1 11 2600 88 70 74 1 799 0 97 2800 82 75 79 1 528 0 85 3000 76 80 84 1 304 0 74 3200 71 85 89 1 118 0 65 3400 67 90 94 0 962 0 57 3600 63 95 99 0 831 0 50 3800 60 100 or above 0 698 0 43 4000 57 NOTES 1 The resolution of a timer count is 64us Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 Freescale Semiconductor 21 Implementation Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 22 Freescale Semiconductor Temperature Sensor Measurement Appendix A Schematic ano IOMLNOO aaas MOT TAA z 1 z BIASA 64 1 B 6 HOLOANNOD dor and n v AS ano dak UNS z TIVH apad E I Xazzna vd Nazwusosus Sx sv SSA vA vV ada oe W TH Twd 09x8 0u ev E SAE wz 4 V 03 0Vda 1S4 7A4 Z Vd T TNE 3T Lub ota AS aNd vZ00LSUN Ta a INT
19. TimingLoop jmp otorHang If no HALL output Stop the driving HallFound mov TIMCNT DriveTime cbega 20 StableDrive mov MaxDeadTime DriveTime StableDrive lda DeadTime add DriveTime sta ActualPeriod ele PTAD Disconnect coil mov MKBISC_KBACK KBISC Clear Flag and mask interrupt mov mMMTIMSC_TSTP mMTIMSC_TRST MTIMSC mask interrupt and clear flag Ges Read Temperature S Timer prescalar 8 Bus 2MHz Max OF period 1 02ms Timer resolution 4us VS n O K lt G 0 Timer clk 250kHz ReadSensor mov MTIM_BUS_CLK MTIM_DIV_8 MTIMCLK Change Timer resolution mov 63 MTIMMOD OF period mov mMMTIMSC_TRST mMTIMSC_TOIE MIIMSC Reset and Start Timer mov mACMP SC_ACME mACMPSC_ACIE ACMP_OUTPUT_RAISING ACMPSC Enable ACMP start RC rise bset ACMPSC_ACF ACMPSC Clear ACMP Flag wait delay to OF and make the read process deterministic brcelr ACMPSC_ACF ACMPSC NoReading mov MTIMCNT SensorReading bset ACMPSC_ACF ACMPSC Clear ACMP Flag clr ACMP SC disable ACMP wait mov mMMTIMSC_TSTP mMTIMSC_TRST MTIMSC mask interrupt and clear flag mov MTIM_BUS_CLK MTIM_DIV_256 MTIMCLK Reset Timer resolution rts Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 30 Freescale Semiconductor Temperature Sensor Measurement NoReading mov 500 SensorReading Smallest Number ele ACMPSC disable ACMP mov mMMTIMSC_TSTP mMTIMSC_TRST MTI
20. Variable Speed DC Fan Control using the MC9RS08KA2 Designer Reference Manual RS08 Microcontrollers DRM079 Rev 0 5 2006 9 freescale com 2 freescale semiconductor Variable Speed DC Fan Control using the MC9RS08KA2 Designer Reference Manual by Vincent Ko Freescale Semiconductor Inc Hong Kong To provide the most up to date information the revision of our documents on the World Wide Web will be the most current Your printed copy may be an earlier revision To verify that you have the latest information available refer to http www freescale com The following revision history table summarizes changes contained in this document For your convenience the page number designators have been linked to the appropriate location Revision History Revision Par Page Date Level Description Number s 05 2006 0 Initial release N A Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 Freescale Semiconductor 3 Revision History Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 4 Freescale Semiconductor Table of Contents Chapter 1 Introduction 1 1 l Oj I stated iaa ss di 1 2 Freescale s New Generation Ultra Low Cost MCU 1 3 DC Fan Reference Design Tamel 00 dE 1 4 Bi Phase BLDC Motor ite ce Sem A a dat lass Chapter 2 Motor Control 2 1 CONOR Suysa II TASS Od eae eee 2 2 Roior POSO cris a edd de da dd i AAA e e ARTES d 2
21. d DC Fan Control using the MC9RS08KA2 Rev 0 26 Freescale Semiconductor Temperature Sensor Measurement TargetPeriod ds b 1 ActualPeriod ds b 1 DriveTime ds b 1 SensorReading ds b 1 MotorRunning ds b 1 org RAMStart L L variable data section org ROMStart code section main Entry r T L f L Config ICS Device is pre trim to 16MHz ICLK frequency TRIM value are stored in 3FFA 3FFB mov HIGH_6_13 NV_ICSTRM PAGESEL mov MAP_ADDR_6 NV_FTRIM ICSSC S3FFB mov MAP_ADDR_6 NV_ICSTRM ICSTRM 3FFA mov FICS_DIV_2 ICSC2 Use 4MHz Config System L L mov HIGH_6_13 SOPT PAGESEL Init Page register mov mSOPT_COPT mSOPT_STOPE MAP_ADDR_6 SOPT BKGD disable COP disabled mov mSPMSC1_LVDE mSPMSC1_LVDRE MAP_ADDR_6 SPMSC1 LVI enable mov RTI_128MS MAP_ADDR_6 SRTISC 128ms RTI Init RAM mov MaxDeadTime DeadTim mov 232 TargetPeriod 1000 rpm mov 232 ActualPeriod 1000 rpm GLE SensorReading ein MotorRunning Config GPIO RC init L Buzzer init L PWMn PWMp init L clr PTAD Initial low mov mRC mPWM1 mPWM2 PTADD Set Output pins Config KBI lda mHALL Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 Freescale Semiconductor 27 Implementation KBIES KBIPE sta sta KBI Enable HALL rising Edge Trigger 7 Config MTIM r Timer prescalar 256 gt Timer clk 16kH
22. different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each customer application by customer s technical experts Freescale Semiconductor does not convey any license under its patent rights nor the rights of others Freescale Semiconductor products are not designed intended or authorized for use as components in systems intended for surgical implant into the body or other applications intended to support or sustain life or for any other application in which the failure of the Freescale Semiconductor product could create a situation where personal injury or death may occur Should Buyer purchase or use Freescale Semiconductor products for any such unintended or unauthorized application Buyer shall indemnify and hold Freescale Semiconductor and its officers employees subsidiaries affiliates and distributors harmless against all claims costs damages and expenses and reasonable attorney fees arising out of directly or indirectly any claim of personal injury or death associated with such unintended or unauthorized use even if such claim alleges that Freescale Semiconductor was negligent regarding the design or manufacture of the part Freescale and the Freescale logo are trademarks of Freescale Semiconductor Inc All other product or service names are the property of their respective owners O Freescale Semiconductor Inc 2006 All rights reserved ey
23. e DC fans are of the constant air flow design As the high performance electronic products continue to increase cooling requirement becomes more and more sophisticated MCU approach provides a cost effective solution to this application There are several advantages of a MCU based design over traditional solutions 1 Instead of having a constant air flow the MCU provides enough processing power to modify the fan speed according to environment changes such as the temperature of the target system 2 Fault detection can easily be implemented by the MCU For example the MCU can detect for the air flow blocking or motor jam the motor driver can be stopped completely to avoid further damage 3 Buzzer alarm or digital output acknowledgement can be generated under the faulty situation The MCU chosen for this purpose must be low cost and it must provide small geometry package to integrate into the fan controller printed circuit board PCB The MC9RS08KA2 is ideal for this application Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 Freescale Semiconductor 7 Introduction 1 2 Freescale s New Generation Ultra Low Cost MCU The MC9RS08KA2 microcontroller unit MCU is an extremely low cost small pin count device for home appliances toys and small geometry applications such as a DC fan controller This device is composed of standard on chip modules including a very small and highly efficient RS08 CPU core 62 bytes RAM 2K bytes FLASH
24. each commutation step reading of the temperature sensor contributes a delay to the actual dead time duration This delay is deterministic such that the software control loop can easily deduce the actual speed of the motor Hence this delay can be considered as a part of the total dead time delay for each commutation Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 16 Freescale Semiconductor Control Loop START TargetPWMPeriod Longest Continuously monitor the hall sensor output ActualPWMPeriod Longest P s sai a z i di i aaa a A ed gt Energize L1 L2 I DriveL1 22277 Start Timer t a in is SE De energize Coils I Drive L2 7 7 Stop Timer lt eta Fault Record DriveTime condition I detected I I bes a i peri Sound Buzzer De energize Coils pe See E E s i During the dead time delay update PWM period for the next commutation od k AE z s PE e ai SEE S Modify Target PWM period value Update TaraetPWMPeriod every 128ms based on temperature P 9 reading Figure 3 2 Firmware Control Loop Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 Freescale Semiconductor 17 Implementation 3 4 Temperature Sensor Measurement The temperature sensor measurement is performed based on the methodology of an emulated ADC described in the application note AN3266 Getting Started with RS08
25. equ 40 ICS_DIV_4 equ 80 ICS_DIV_8 equsc0 MTIM Definition MTIM_DIV_1 equ 00 MTIM_DIV_2 equ 01 MTIM_DIV_4 equ 02 MTIM_DIV_8 equ 03 MTIM_DIV_16 equ 04 MTIM_DIV_32 equ 05 MTIM_DIV_64 equ 06 MTIM_DIV_128 equ 07 MTIM_DIV_256 equ 08 MTIM_BUS_CLK equ 00 MTIM_XCLK equ 10 Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 Freescale Semiconductor 25 AI as v Implementation MTIM_TCLK_FALLING equ 20 MTIM_TCLK_RISING equ 30 L ACMP Definition ACMP_OUTPUT_FALLING equ 00 ACMP_OUTPUT_RAISING equ 01 ACMP_OUTPUT_BOTH equ 03 RTI Definition RTI_DISABLE equ 00 RTI_8MS equ 01 RTI_32MS equ 02 RTI_64MS equ 03 RTI_128MS equ 04 RTI_256MS equ 05 RTI_512MS equ 06 RTI_1024MS equ 07 L Application Definition L RC equ PTAD_PTADO mRC equ mPTAD_PTADO TEMPSEN equ PTAD_PTAD1 mTEMPSEN equ mPTAD_PTAD1 HALL equ PTAD_PTAD2 mHALL equ mPTAD_PTAD2 BUZZER equ PTAD_PTAD3 mBUZZER equ mPTAD_PTAD3 PWM2 equ PTAD_PTAD4 mPWM2 equ mPTAD_PTAD4 PWM1 equ PTAD_PTAD5 mPWM1 equ mPTAD_PTAD5 MinDeadTime equ 2 MaxDeadTime equ 150 TableStart equ 00003E00 L Application Macro StartTimer macro mov DeadTime MTIMMOD OF period mov mMTIMSC_TRST mMTIMSC_TOIE MTIMSC Reset and Start Timer endm org TINY_RAMStart variable data section DeadTime ds b 1 Variable Spee
26. ge to the new value gradually 2 5 Motor Startup In this DC fan application it is desirable to only allow the motor to operate in an uni direction such that the airflow to the target system will always be in one direction With the bi phase motor design it is difficult to guarantee the direction of rotation Commutation order or the coil energizing sequence happens to be the same for both directions of rotation The rotor position or axis must initially be known in order to guarantee the direction of rotation When the first commutation step is activated where the adjacent coil pair to the initial axis is energized the rotor starts to move Since the adjacent coil pairs are connected together and energized at the same time there are equal pulling pushing force induced on the rotor in both directions There is chance for the rotor to startup in either direction It is necessary to monitor the initial direction of rotation If the direction is not correct the motor must be locked back to the startup axis again and the commutation step repeated The direction of rotation can be detected by the Hall sensor output If the initial rotor axis is known the output edge polarity rising edge or falling edge determines the direction of rotation In the modern bi phase motor design the direction of rotation is normally defined by the manufacturer The stator design is not symmetric such that the motor will have a high tendency to rotate in one direction than
27. s s Reset Vector r s o o o o oe oe oe ao o o s s o o o oe o o o o o o o s o o9 o o o o oa o9 o o9 oa o o o o o oa oo o oe oe oe o oe oe oe oe oe oe oe oe o o o oe 3ffc org Security SFF b dc main jmp Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 Freescale Semiconductor 32 How to Reach Us Home Page www freescale com E mail support freescale com USA Europe or Locations Not Listed Freescale Semiconductor Technical Information Center CH370 1300 N Alma School Road Chandler Arizona 85224 1 800 521 6274 or 1 480 768 2130 support freescale com Europe Middle East and Africa Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen Germany 44 1296 380 456 English 46 8 52200080 English 49 89 92103 559 German 33 1 69 35 48 48 French support freescale com Japan Freescale Semiconductor Japan Ltd Headquarters ARCO Tower 15F 1 8 1 Shimo Meguro Meguro ku Tokyo 153 0064 Japan 0120 191014 or 81 3 5437 9125 support japan freescale com Asia Pacific Freescale Semiconductor Hong Kong Ltd Technical Information Center 2 Dai King Street Tai Po Industrial Estate Tai Po N T Hong Kong 800 2666 8080 support asia O freescale com For Literature Requests Only Freescale Semiconductor Literature Distribution
28. the other However the direction of rotation cannot be guaranteed without proper monitoring techniques in place 2 6 Fault Detection Motor fault is identified as the rotor not moving which is normally the case when the rotor is jammed may be cause by blocked airflow During each commutation step the Hall sensor output is monitored If it is not toggled within a defined duration commutation sequence is terminated all coils are de energized In this design when a motor fault occurs a buzzer is activated as the alarm Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 Freescale Semiconductor 13 Motor Control Variable Speed DC Fan Control using the MC9RS08KA2 Rev 0 14 Freescale Semiconductor Block Diagram Chapter 3 Implementation 3 1 Block Diagram The block diagram of the DC fan design is illustrated in Figure 3 1 A 12V low cost bi phase BLDC motor is used in this application The MCU performs alternate outputs to the two NPN transistors that drive the motor coils Open drain output Hall sensor is required and positioned close the rotor The device responds to magnetic field changes during the motor operation digitizing output feedback of the rotor position to the MCU for close loop motor control and fault detection Ambient temperature information is measured from an external temperature sensor In the faulty situation such as motor jam the buzzer alarm is driven by the MCU through a pulse width modulated
29. tor 11 Motor Control 2 3 Commutation Waveforms In general in a bi phase motor design alternate coils are tied together and give a single connection to the driver In this design the driver connection for coil A and coil C is called L1 see Figure 2 1 Similarly the driver connection for coil B and coil D is called L2 Driving to either of the connections will energize a coil pair The commutation waveform is shown in Figure 2 2 The coil driving period is aligned with the Hall sensor output When the sensor output toggles coil driving is stopped the coils are de energized for a period of time before the next coil pair is energized Dead Dead Dead Dead Dead Zone Zone Zone Zone Zone Li n p gt t L2 p gt t Hall Output p t lt 90 of rotation Figure 2 2 Bi Phase BLDC Motor Commutation Waveform 2 4 Speed Control Motor speed is normally defined as the mechanical revolution per one minute of time rpm In electrical terms one commutation contributes to 90 degrees of a revolution Thus control the time taken per commutation can effectively control the overall speed One commutation step includes a dead time where the coils are not energized and the coils energization time The whole commutation period could be considered as a pulse width modulation PWM output cycle The PWM period defines the motor speed in this case The coils energization time is in fact the PWM driving period
30. z Bus 4MHz Max OF period 16 384ms Timer resolution 64us MTIM_BUS_CLK MTIM_DIV_256 4255 MTIMMOD mov mov MTIMCLK r Motor Start Sequence r ResetPosition mov mPWM1 PTAD lda 30 Dlyl bsr Delay dbnza Dlyl G Ly PTAD bsr Delay Drive L2 ldx mPWM2 bsr Set PWM bsr Delay inc MotorRunning Lock FAN in reset position for Delay 0 5s de energize coils Select L2 Coils Drive coil De energize coils otherwise Update Software flag Fan Control Loop E FanControlLoop 1 Drive Ll coil ol a KBIES HALL falling edge trigger ldx mPWM1 Select LL Coil bsr SetPWM Drive coil 2 Read Temp Sensor jsr ReadSensor Read Sensor value 3 Dead time control StartTimer Wait dead time period wait mov mMMTIMSC_TSTP mMTIMSC_TRST MTIMSC mask interrupt and clear flag 4 Drive L2 coil bset HALL KBIES HALL rising edge trigger ldx mPWM2 Select L2 Coil bsr SetPWM Drive coil Variable Speed DC Fan Control using the MC9RSO8KA2 Rev 0 28 Freescale Semiconductor Temperature Sensor Measurement 5 Read Temp Sensor Again bsr ReadSensor Read Sensor value 6 Dead time control StartTimer 7 During the dead time update dead time period every 128ms brclr SRTISC_RTIF MAP_ADDR_6 SRTISC UpdateLater Update PWM duty cycle jsr TableLookup UpdateLater lda ActualPeriod sub TargetPeriod Actual Target blo IncPeriod
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