M16C/26 APPLICATION NOTE Writing Interrupt Handlers in C
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1. ENESAS APPLICATION NOTE M16C 26 Writing Interrupt Handlers in C 1 0 Abstract This application note describes how to write hardware and software interrupt handlers using NC30 C version 4 XX and earlier compiler for M16C microcontrollers Interrupt mechanisms are processor hardware specific the ANSI C specification for writing interrupt functions is at best vague 2 0 Introduction The Renesas M30262 is a 16 bit MCU based on the M16C 60 series CPU core The MCU features include up to 64K bytes of Flash ROM 2K bytes of RAM and 4K bytes of virtual EEPROM The peripheral set includes 10 bit A D UARTs Timers DMA and GPIO In order to process interrupts your program must do two things 1 Properly declare the function handling the interrupt 2 Set the appropriate interrupt vector to point to the function 3 0 Hardware Interrupts By declaring the function as an interrupt handler the compiled output ends in a reit return from interrupt instruction rather than the standard rts return from subroutine For hardware interrupts use the declaration pragma INTERRUPT function name B Note INTERRUPT must be uppercase and the prototype void function name void Obviously a hardware interrupt can neither be passed a value nor return a value Section 5 0 gives an example hardware interrupt processing program Note the B option in the pragma statement This option speeds up interrupt response2. approved destination Any diversion or reexport contrary to the export control laws and regulations of Japan and or the country of destination is prohibited Please contact Renesas Technology Corporation for further details on these materials or the products contained therein
3. of nonflammable material or iii prevention against any malfunction or mishap Notes regarding these materials These materials are intended as a reference to assist our customers in the selection of the Renesas Technology Corporation product best suited to the customer s application they do not convey any license under any intellectual property rights or any other rights belonging to Renesas Technology Corporation or a third party Renesas Technology Corporation assumes no responsibility for any damage or infringement of any third party s rights originating in the use of any product data diagrams charts programs algorithms or circuit application examples contained in these materials All information contained in these materials including product data diagrams charts programs and algorithms represents information on products at the time of publication of these materials and are subject to change by Renesas Technology Corporation without notice due to product improvements or other reasons It is therefore recommended that customers contact Renesas Technology Corporation or an authorized Renesas Technology Corporation product distributor for the latest product information before purchasing a product listed herein The information described here may contain technical inaccuracies or typographical errors Renesas Technology Corporation assumes no responsibility for any damage liability or other loss rising from these inaccuracies or erro
4. by switching to CPU register Bank 1 Without this switch the compiler generates code to stack all registers used by the interrupt functions Be careful when using this option if using an RTOS or nested interrupts REU05B0038 0100Z June 2003 Page 1 of 4 M16C 26 E E M ESAS Writing Interrupt Handlers in C 4 0 Reference Renesas Technology Corporation Semiconductor Home Page http www renesas com E mail Support support apl renesas com Data Sheets e M16C 26 datasheets M30262eds pdf User s Manual e M16C 20 60 C Language Programming Manual 6020c pdf e M16C 20 60 Software Manual 6020software pdf e MSV30262 SKP Quick start guide Auick Start Guide MSB30202 pdf e MSV30262 SKP Users Manual Users Manual MSV30262 pdf 5 0 Software Code The example program was written to run on the MSV30262 Starter Kit but could be modified to implement in a user application The program was compiled using the KNC30 compiler The program demonstrates using the interrupt to invoke relevant service routine Interrupt signals are generated by pressing any of the user pushbutton switches S2 S3 or S4 on the SKP board The program accepts incoming interrupt signals in 3 of the 4 Key Input Interrupt pins Relevant interrupt service routine is invoked to toggle the red LED D3 of the SKP board If the red LED was ON then pressing any of the 3 switches will turn it OFF and vise versa 8 RK RK HK KK eK HK kkk kkk kkk kkk kkk kkk kkk kkk kkk k kkk k
5. he remaining unused Key Input port pin to output for avoiding undesirable low input signal that may cause unwanted interference return Now the second part of the process is to set up the interrupt vector Included with the compiler is the startup file sect30 inc Open this file and near the end the interrupt vectors are declared The assembler function label is 19 the C function name preceded by an underscore First define the label as global using the glb pseudo instruction then replace the dummy_int label at the appropriate table entry see sample code below For our example program given above we need to edit the Key Input Interrupt vector commented as key on wakeup for user lword dummy int DMAO for user lword dummy int DMA1 for user glb _KeyInput_ ISR lword KeyInput ISR Key on wakeup for user lword dummy int AD Convert for user REU05B0038 0100Z June 2003 Page 4 of 4 Keep safety first in your circuit designs Renesas Technology Corporation puts the maximum effort into making semiconductor products better and more reliable but there is always the possibility that trouble may occur with them Trouble with semiconductors may lead to personal injury fire or property damage Remember to give due consideration to safety when making your circuit designs with appropriate measures such as i placement of substitutive auxiliary circuits ii use
6. k k k k k k k k k kkk k k k kk k k k k k k k k k File Name main c Content This program toggles the red LED D3 with successive pressing of any of the three switches 2 3 or 4 With each pressing of a switch a key input interrupt 1S generated and toggles the red LED from ON to OFF or vise versa X Date 11 13 2002 This program was written to run on the MDECE30262 Board for MSV30262 SKP Copyright 2003 Renesas Technology America Inc All rights reserved REU05B0038 0100Z June 2003 Page 2of 4 M16C 26 E E N ESAS Writing Interrupt Handlers in C j SLog include str262 h M16C 26 special function register definitions pragma INTERRUPT B KeyInput ISR LEDs define red led p7 0 define yellow led p7 1 define green led p7 2 void KeyInput ISR void declare interrupt service routine void mcu init void declare mcu initialization routine KK KK KK eR HK KK eK IK k kk k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k OR k k k k k k k k k k Name main Parameters None Returns None Description main program loop kkkkk kk kik kikk kiikikkixkikikikikkikiikikkikikxkiikikikikikkikikikikkikikikkik x main 1 meu init initialize MCU kupic 2 set key input interrupt level 2 _asm fset i enable interrupts while 1 wait for interrupt Axx k kkk kkk kkk kkk kkk kkk kk kkk kkk kkk kkk kkk k
7. kk k kk k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k Name KeyInput ISR Parameters None Returns None Description This is the service routine for Key Input Interrupt This routine will be called whenever any of the switches S2 S3 or S4 is pressed kkkkk kk kik kikk kiikikkixkikiikikkikiikikikikikxkikkikkikikkikikikikk ikikikkik x void KeyInput ISR void Toggle red LED asm Eset i enable interrupt for the ROM monitor if red led 1 check if red LED is OFF red led 0 Turn red LED ON else Otherwise red LED is ON red led 1 Turn red LED OFF REU05B0038 0100Z June 2003 Page 3 of 4 M16C 26 E E M ESAS Writing Interrupt Handlers in C 8K RK HK KK eK HK KK kkk kkk kkk kkk kkk kkk kkk kk k kk k k k kk k k k k k k k k k k k k k k k k k k k k k k k k k k k Name MCU init Parameters None Returns None Description Routine for initializing the LEDs of the SKP board MSV30262 And the port pins of Key Input Interrupt A Ak ea ek A eA eR IK IK IK I I I I IK IR I I I I I IO Ke void mcu_init void LED initialization par O 1 set LED ports to outputs connected to LEDs pd7 l 1 pd7 2 1 red led 1 turn off LEDs green led 1 yellow led 1 Configure port pins for Key Input Interrupt pdl0 5 0 set Key Input port pins of switches 2 3 and 4 to inputs xy pdl0 6 0 pdl0 7 0 pdio 4 1 set t
8. rs Please also pay attention to information published by Renesas Technology Corporation by various means including the Renesas Technology Corporation Semiconductor home page http www renesas com When using any or all of the information contained in these materials including product data diagrams charts programs and algorithms please be sure to evaluate all information as a total system before making a final decision on the applicability of the information and products Renesas Technology Corporation assumes no responsibility for any damage liability or other loss resulting from the information contained herein Renesas Technology Corporation semiconductors are not designed or manufactured for use in a device or system that is used under circumstances in which human life is potentially at stake Please contact Renesas Technology Corporation or an authorized Renesas Technology Corporation product distributor when considering the use of a product contained herein for any specific purposes such as apparatus or systems for transportation vehicular medical aerospace nuclear or undersea repeater use The prior written approval of Renesas Technology Corporation is necessary to reprint or reproduce in whole or in part these materials If these products or technologies are subject to the Japanese export control restrictions they must be exported under a license from the Japanese government and cannot be imported into a country other than the
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