Embedded C Programming II (ECProgramII)
Contents
1. Table 3 Port Register Name Abbr R W Initial Value Address Port Data Register 9 PDR9 R W H FF H FFDC Port Mode Register 9 PMR9 R W H FFEC void init_io void Setting for General Application P_IO PCR3 BYTE 0x00 P37 P31 inputs P_IO PUCR3 BYTE 0x00 Turn off the MOS pull up PMR3 IAEVLIAEVHI I TMOFHITMOFLI AEVL 0 P37 as I O AEVH 0 P36 as I O TMOFH 0 P32 as I O TMOFL 0 P31 as I O P_IO PMR3 BYTE 0x00 PMR9 I I IPIOFFI IPWM2IPWM 11 PIOFF 0 large current port step up circuit is turned on PWM1 PWM2 0 P90 and P91 functions as P_IO output pin P_IO PMR9 BYTE OxFO set_imask_ccr 0 AN0403001 Rev 1 00 March 2004 Page 8 of 21 PRELIMINARY tENESAS iat Embedded C Programming II ECProgramll 2 2 3 Initialization of Serial Port The init_sci routine is to initialize the Serial port This routine can be integrated with the init_io routine This function set the serial port to operate at Asynchronous mode at 9600 baud rate The following are the relevant registers for serial port initialization Table 4 Serial Port Register Name Abbr R W Initial Value Address Serial Mode Register SMR R W H 00 H FFA8 Bit Rate Register BRR R W H FF H FFA9 Serial Control Register SCR3 R W F 00 H FFAA Transmit Data Register TDR R W H FF H FFAB Serial Status Regi2. C source file PintPRG en H E Assembly source file 000000800 P Modify E Linkage symbol file c C DSEC ew Overlay ESESEC New Overlay D Ox00600000 Pextmem Femove 4 2x Down Figure 4 HEW Section Setting The section can be declared in the Section Category of the Link Library tab Place the cursor at the Address Column and Click on Add button o Key in the Address H 60 0000 Place the cursor at the Section Column and Click on Add button o Key in the section name Pextmem Place the cursor at the Section Column and Click on Add button The above steps will ensure that the compiled program will be located in the designated area o Key in the section name Cextmem To verify the output the map file can be generated List Category of the Link Library tab P 00000800 000008e1 e2 2 C DSEC 000008e2 000008ed 2 C BSEC 000008ee 000008f5 8 2 D 000008f6 000008f9 4 2 Pextmem 00600000 00600003 4 2 Cextmem 00600004 00600009 6 2 B OOffef10 OOfff32f 420 2 R OOff 330 OOff 333 4 2 S OOfffd00 OOfffeff 200 2 Figure 5 HEW Generated Map File AN0403001 Rev 1 00 March 2004 Page 15 of 21 PRELIMINARY tENESAS et Embedded C Programming II ECProgramll 3 1 2 Bus State Controller BSC Both the hardware and linker must be set correctly However the access to the external memory may not be successful unless the bus st
3. sci_charput E sci_charput L sci_charput P sci_charput void sci_charput char OutputChar Serial Port while P_SCI3 SSR BIT TDRE 0 P_SCI3 TDR OutputChar P_SCI3 SSR BIT TDRE 0 The routine checks for the ready flag before it sends the variable OutputChar to the serial buffer 2 2 6 Summary amp Improvement The program does not have many tasks Therefore the polling method to check for the intruder and switch may not cause many resources wastage If too many tasks are executing it may be wise to use interrupt to signify an intruder access The sending of message through the polling method is also taking up much CPU time The serial port is operating at 9600bps The interrupt method may be more efficient In this example the bouncing effect of the switch is ignored The debouncing can be improved using software mean by performing a double check AN0403001 Rev 1 00 March 2004 Page 12 of 21 PRELIMINARY f 2 HEW i EN ESAS Embedded C Programming II ECProgramll 3 Access of External Memory For lower end MCUs such as the SLP which have no external bus interface usage of serial interface protocol to access external memory will be preferred as this uses lesser pin count The common memory used is IC or SPI E PROM If such interface peripheral is not available programmer will need to write the algorithm based on the interface and memory specification Please re
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5. 1 0 16 9600 0 25 0 16 19200 0 12 0 16 31250 0 4 0 0 7 0 AN0403001 Rev 1 00 March 2004 Page 10 of 21 PRELIMINARY tENESAS T Embedded C Programming lI ECProgramll 2 2 4 Main Routine The main routine is executed after the reset routine The input output port and serial port are initialized before the infinite loop is entered The program will check for intruder Port 3 and switch Port 31 Once condition is met the respective action will be executed lt machine h gt is included as the intrinsic function set_imask_ccr is used include iodefine h include lt machine h gt void send_message void void sci_charput char OutputChar void init_sci void void init_io void void abort void void main void unsigned int delay init_io init_sci P_IO PDR9 BYTE OxFF Turn off All LED while 1 if P_IO PDR3 BIT P30 detected intrusion P_IO PDR9 BIT P92 0 Turn on alarm LED send_message call for help through serial port if P_IO PDR3 BIT P31 clear alarm P_IO PDR9 BIT P92 1 Turn off alarm LED AN0403001 Rev 1 00 March 2004 Page 11 of 21 PRELIMINARY tENESAS T Embedded C Programming II ECProgramll 2 2 5 Send Message The following two routines are to send message in the form of character to the external world via the serial port void send_message void sci_charput H
6. CProgramll ISPCR I ISPC32I ISCIN V3ISCIN V2I I I 1111111010101010 SPC32 1 P42 functions as TXD32 output pin meed to set TE bit in SCR3 after setting this bit to 1 ISCINV3 0 TXD32 output data is not inverted SCINV2 0 RXD32 input data is not inverted Bits 7 and 6 are reserved and always read as 1 Bits 4 1 and 0 are reserved and only 0 can be written to these bits P_SCI3 SPCR BYTE OxE0 SSR_ ITDREIRDRFIOERIFERIPERITENDIMPBRIMPBTI TDRE transmit data register empty RDREF receive data register full OER overrun error FER framing error PER parity error TEND transmit end MPBR Multiprocessor bit receive MPBT Multiprocessor bit transfer P_SCI3 SSR BYTE 0x84 Mnitialise upon reset to 0x84 In this peripheral initialization calculation of the parameter is required N for BRR is calculated based on N OSC 1 64 x 2 x B Where B Bit rate bit s N Baud rate generator BRR setting 0 lt N lt 255 OSC Value of osc Hz n Baud rate generator input clock number n 0 2 or 3 Table 5 SCI setting for N and n OSC 10 MHz 16 MHz Bit Rate Error Error bit s n N n N 110 2 88 0 25 2 141 02 150 2 64 0 16 2 103 0 16 200 2 48 0 35 2 11 0 16 250 2 38 0 16 2 64 0 79 300 2 51 0 16 600 2 25 0 16 1200 0 129 0 16 0 207 0 16 2400 0 64 0 16 0 103 0 16 4800 0 5
7. CR3 he AN0403001 Rev 1 00 March 2004 Page 6 of 21 tENESAS PRELIMINARY HEW Embedded C Programming II ECProgramll union PMR9 unsigned char BYTE Byte Access struct Bit Access unsigned char 4 unsigned char PIOFF 1 PIOFF unsigned char 1 unsigned char PWM2 1 PWM2 unsigned char PWM1 1 PWM1 BIT fF PMR9 i b rr define P_SCIB volatile struct st_sci3 0x0000FF91 define P_IO volatile struct st_io OxOOOOFFC8 el SCI3 Address I O Address Observation The structure union declaration is based on the information provided in the MCU hardware user manual Refer to Figure 1 The volatile keyword is used in the declaration for all the peripherals and ports The structure union declaration will enable the use of bit manipulation assembly instruction AN0403001 Rev 1 00 March 2004 Page 7 of 21 PRELIMINARY tENESAS T Embedded C Programming II ECProgramll 2 2 2 Initialization of Port Itis essential to initialize the hardware peripherals at power up state o This routine can be called either in the reset routine if it is critical to setup the peripherals early or main routine HEW will generate a Hardware_Setup function if this feature is enabled in the project generation In this example a init_io routine is written to o Initialize the Port 3 and 9
8. ELIMINARY HEW Embedded C Programming II ECProgramll Please refer the detail of HEW code generation in Application Note HEW Code Generation or HEW user s manual In this example only the main project C file will be modified 2 2 1 Port and Peripheral Definition File The following is extracted from the iodefine h struct st_io union struct I O PDR3 unsigned char BYTE Byte Access struct Bit Access unsigned char P37 1 P37 unsigned char P36 1 P36 unsigned char P35 1 P35 unsigned char P34 1 P34 unsigned char P33 1 P33 unsigned char P32 1 P32 unsigned char P31 1 P31 unsigned char P30 1 P30 BIT PDR3 ps union PDR9 unsigned char BYTE Byte Access struct Bit Access unsigned char 2 i unsigned char P95 1 P95 unsigned char P94 1 P94 unsigned char P93 1 P93 unsigned char P92 1 P92 unsigned char P91 1 P91 unsigned char P90 1 P90 BIT PDR9 ps union PCR3 unsigned char BYTE Byte Access struct Bit Access unsigned char PCR37 1 PCR37 unsigned char PCR36 1 PCR36 unsigned char PCR35 1 PCR35 unsigned char PCR34 1 PCR34 unsigned char PCR33 1 PCR33 unsigned char PCR32 1 PCR32 unsigned char PCR31 1 PCR31 unsigned char PCR30 1 PCR30 BIT P
9. EXT_DATA_PTR unsigned long 0x0600000 Area 3 Address Programmer can read or write the external memory seamlessly Read_data EXT_DATA Read_data EXT_DATA_PTR 4 3 1 3 2 Copy Memory from Section to Section The following provides an alternative method to copy code data from one area to another These may be done for Faster execution in an area copy from E2PROM to DRAM Flashing purposes copy from flash to internal RAM Copy contents from section Source to section Destination char S_TOP char S_END __sectop char D_TOP sheend void copy_section void char p q S_TOP char __sectop Source S_END char __secend Source D_TOP char __sectop Destination for p S_TOP q D_TOP p lt S_END p q xaz p q Pp To enable easy debugging programmers may like to use the overlay feature that is available in HEW AN0403001 Rev 1 00 March 2004 Page 17 of 21 PRELIMINARY f 2 HEW bs EN ESAS Embedded C Programming II ECProgramll 3 1 3 3 Execution of External Function The following are examples of external function calling methods i Function pointer with no passing parameter typedef void extFnPtr void define EXT_ADDR_PTR 0x0600000 define EXT_FN_PTR_ADDR unsigned long EXT_ADDR_PTR static const extFnPtr Ext_Fn extFnPtr EXT_FN_PTR_ADDR Ext_Fn Call the e
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12. at the relevant code and data are to be stored in a specific area In this case the external memory is located at area 3 Assuming that the external memory is a ROM and a program section and a constant section are to be stored There are two steps to achieve this 1 In the project file Declare the section pragma section extmem const char ExtData hello int total int a int b pragma section return a b In this case Data ExtData and Function total are declared within the section extmem The Linker will look for Cextmem Constant and Pextmem Program section declarations NOTE if other variables are declared the linker will look for the respective sections AN0403001 Rev 1 00 March 2004 Page 14 of 21 tENESAS 2 In HEW section setting PRELIMINARY HEW Embedded C Programming II ECProgramll Hitachi H8S H8 300 Standard Toolchain Configuration Debug 7 Category EES Cextmem Ox0OFFEF10 Import Export Up Optiuris Link Libray noprelink rom D R nomessage list CONFIGDIR PROJECT NAME map show symbol teference nooptimize start Oo C C Assembly Link Library Standard Library CPU 4 gt G All Loaded Projezts F f Section J Oo es Show entries for Section Ne C source file A Address Section Add
13. ate controller is properly initialized The following are the key points to note when memory connection is concerned i Wait states 1 5 Software wait states or hardware wait state ii Bus width 8 or 16 bit depending on operating mode access area amp setting iii Area iv Refresh cycle For DRAM These settings must match the hardware wiring and memory characteristic 3 1 3 Code amp Data Access Method The current example has shown one example of external memory accessed The extmem section contain ROM based data and code Thus users have to split their final compiled project into two parts in order to program into the MCU amp external ROM a H8 3048 internal ROM b External ROM Main routine Internal ROM H8 300H MCU Memory Map H8 300H MCU External routine External ROM Figure 6 Illustration of Mapping amp Physical device The other possible scenarios are 1 Needs to access Data in external memory area a This can be a external ASIC containing data 2 MCU will copy the compiled code from one area to another area for faster execution a EEPROM to DRAM b Internal ROM to Internal RAM AN0403001 Rev 1 00 March 2004 Page 16 of 21 PRELIMINARY f 2 HEW bs EN ESAS Embedded C Programming II ECProgramll 3 1 3 1 Access External Data By making a pointer to the external address space define EXT_DATA unsigned long 0x0600000 Area 3 Address define
14. cs and storage areas Utilization of Stack and Heap Usage of preprocessor directives Macro conditional compilation and etc Usage of Extended functions Pragma intrinsic functions and etc Usage of available library Effect of a function call on the stack and registers Management of section by HEW Comparison of similar operation Information on flow of project compilation linking and debugging Suggested programming techniques In this second part of Embedded C programming the emphasis is on how to control the embedded microcontroller unit MCU to access peripherals ports and external memory AN0403001 Rev 1 00 March 2004 Page 3 of 21 PRELIMINARY f 2 HEW m EN ESAS Embedded C Programming II ECProgramll 2 Access of Peripherals and Ports A microcontroller unit MCU contains the main processor core and other different peripherals to fulfill an application needs Thus the characteristics of each peripheral may not be similar in different MCU 2 1 Timer o 8 bit 16 bit external trigger Serial port o Asynchronous Synchronous VC SPI conformance PWM o 8 bit 10 bit number of channels Port o High current bi directional with pull up enable ADC o 10 bit interrupt trigger multiplex channels General Peripheral Setting The detailed setting of each peripheral is beyond the scope of discussion However the basic accessing method using C program will be highlighted in
15. d Peripheral Definition File cee eeeeeeececeneeceneeeenee cence ceaeeeeaeeeeaeeseaeeeeaeeeeaeeeeaeeseaeeeeaeees 6 2 2 2 intaia oi FPOe E 8 2 2 3 Initialization of Serial Port eseeesseeeseeseeeseesisrrsrssirsinsinsstnstinstinstnnsinstinstnnstnntunstnnntnnttnstnnen nanne 9 224 Mat ROUINO oee n leietcee ne hain nt caaiods 11 200 Sna MoI ea N 12 226 Summary amp IMpProvemMents css sees ieessedes steed seeesteedeeeetees steeds nies debe ede ee 12 3 Access of External M MoOry cccceeesceeccceeceeeeaeeesaeeeaaeeeaaeneaeeneaaeseaaeeeaeeeeaeeneaeeseaeeseaeeneaeeseaeeenenees 13 O 1 SEXaMple PE EE E A dete Ae abana aoe aden ast 14 gii SOCOM DSCIALATION seecisceeiecteateueecctshecesessesadees teley beces veces bones edes ant edad ees attendees ade ieeteses 14 3 1 2 Bus State Controller BSC oo eee eesceeseceeseeeeeee E E E E S S 16 3 1 3 Code amp Data Access Method 0 cece eeeeceeeneeeeneeeeeeeeaeeesaeeeaaeeeeaeeeaaeseaaeeeaeeseaaeseaaeeeaeeseaeeseaeeeaes 16 A CONCUSSION 5 se coc ceeic casts i hate eet teas E O OESS E dt cone daar eke et aes cece Poet eet 19 PRETEEN Eia EEE hs SoS ata cereus ais Sung N E addy ae tee oad catas 19 AN0403001 Rev 1 00 March 2004 Page 2 of 21 PRELIMINARY tENESAS T Embedded C Programming II ECProgramll 1 Recapitulate of Part 1 The topics covered in Embedded C Programming I are Generated C files and sections of HEW Effect of C initialization on each variable characteristi
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18. fer to Application Note on Interfacing to EEPROM with I2C Emulation For higher end MCUs such as the H8 300H which is catered to support external memory programmers will have to make several settings in order to make this external memory work seamlessly with the main system coding H SFFFFF H 600000 External address Area 3 HTFFFFF POP tL H 800000 Figure 2 Area 3 Mapping For the access of external memory other than the physical hardware consideration the following settings are to be considered when accessing external memory Physical hardware interface consideration is not discussed in this document 1 2 Section declaration Bus State Controller BSC Must be initialized before the memory can be used The following are the key points to note when memory connection is concerned i Wait states ii Bus width iii Area iv Refresh cycle For DRAM Access Method AN0403001 Rev 1 00 March 2004 Page 13 of 21 PRELIMINARY f 2 HEW bs EN ESAS Embedded C Programming II ECProgramll 3 1 Example The following example illustrates the settings required to access the external memory Example Table 6 Area 3 Interface Information Memory ROM Area Area 3 of H8 3048 in advanced mode H 60 0000 H 7F FFFF H8 3048 External Memory Figure 3 MCU Interface to ROM 3 1 1 Section Declaration The objective of setting the section is to notify the compiler th
19. ics products or if you have any other inquiries Note 1 Renesas Electronics as used in this document means Renesas Electronics Corporation and also includes its majority owned subsidiaries Note 2 Renesas Electronics product s means any product developed or manufactured by or for Renesas Electronics PRELIMINARY tENESAS APPLICATION NOTE HEW Embedded C Programming II ECProgramll Introduction In this second part of the application note it will emphasize on how to Examples on access of peripherals and external memory are provided to give programmers another perspective of programming in embedded environment The examples used will be based on High performance Embedded Workshop HEW Version 2 SLP TINY C Compiler version 5 0 and H8 SLP amp H8 300H are used as the targets for explanation However this explained fundamental concept would be applicable to other compilers and MCU series Target All AN0403001 Rev 1 00 March 2004 Page 1 of 21 PRELIMINARY f 2 HEW m EN ESAS Embedded C Programming II ECProgramll Contents is Recapiulate of Parm Taracieorereoni cen a aE aE E A EERS A E EERE SAAE 3 2 Access of Peripherals and Ports cicadas val ek eee tees ee edeadedes ede deen etveeseviecsenestes 4 2 1 General Peripheral SOtnGs sccsesseseaccssevesecucsevtesiaeseeves casucvbaecvszetvbeasweesivesdeva newtaiddaatevhadevs he aaaeeneennds 4 2 2 Example anne E ENE EE TE EREE ERE NE 5 221 Port an
20. poration 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 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 AN0403001 Rev 1 00 March 2004 Page 21 of 21
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22. ster SSR R W FH 84 H FFAC Receive Data Register RDR R F 00 H FFAD Transmit Shift Register TSR Protected Receive Shift Register RSR Protected Bit Rate Counter BRC Protected Clock Stop Register 1 CKSTPR1 R W H FF H FFFA Serial Port Control Register SPCR R W H FF H FF91 void init_sci void SCR3 ITIEIRIEITEIREIMPIEITEIEICKE1ICKEOI TIE Transmit interrupt enable RIE Receive interrupt enable TE Transmit enable JIRE Receive enable MPIE Multiprocessor interrupt enable TEIE Transmit end interrupt enable ICKE1 CKE0 0 asynchronous mode internal clock source SCK32 functions as I O port P_SCI3 SCR3 BYTE 0x30 SMR ICOMICHRIPEIPMISTOPIMPICKS LICKSOI 10101010101010101 COM Communication Mode 0 asynchronous mode CHR Character Length 0 character length 8 bits PE Parity Enable 0 parity bit addition and checking disabled PM_ Parity Mode 0 even parity no effect since parity is already disabled STOP Stop Bit Length 0 1 stop bit MP Multiprocessor Mode 0 multiprocessor communication function disabled ICKS1ICKSOI Clock Select 10101 clock source for baud rate generator clk P_SCI3 SMR BYTE 0x00 Startup default to 9600bps n 0 I N 25 for OSC 16 MHz P_SCI3 BRR 25 AN0403001 Rev 1 00 March 2004 Page 9 of 21 PRELIMINARY f 2 HEW m EN ESAS Embedded C Programming II E
23. the latest information AN0403001 Rev 1 00 March 2004 Page 4 of 21 PRELIMINARY f 2 HEW m EN ESAS Embedded C Programming II ECProgramll 2 2 Example The following example is illustrated to highlight the extra care that is required for embedded programming Example Table 1 Intruder Alarm Operation Description Project An Intruder Alarm Description When there is an intrusion Port 39 detected low A message will be sent out through the serial port An Alarm LED will be set and The alarm LED can be cleared via a switch From External Sensor To PC ic 4 Ld scr Disable b RS232 Driver b Switch Figure 1 Block Diagram of an intruder alarm Table 2 Port Usage of intruder alarm Peripherals Condition Function Port 39 Input Intrusion detection Port 3 Input Disable switch Port 9o Output Alarm LED Serial Port 1 Asyn 9600 bps 1 start 8 data 1 stop No parity Communicate Channel Port 9 is used for driving LED as it has a large current drive 25mA for the LED If another port is used a transistor driver will be needed The example uses SLP H8 38024 as the controller By invoking HEW project generation the basic code structure which consists of all peripherals and ports definition will be generated AN0403001 Rev 1 00 March 2004 Page 5 of 21 CtENESAS HEW will generate o Reset routine c o main project c o iodefine h PR
24. this document Generally the setting for each peripheral is straightforward Each peripheral detail can be referred to in each respective section of the hardware manual General highlight of precautious are 1 Some peripherals may be sharing the same pin out of the MCU Thus user must make their decision based on the hardware schematic and MCU characteristic Some peripherals may not be operational under certain operating mode of the MCU Each peripheral may have a few controlling registers Do not miss any of them Some registers may be responsible for few peripherals Thus when accessing one register programmers must be careful not to affect operation of other peripherals NOTE All related registers will be explained in each peripheral section of the hardware manual The same register will be mentioned again in another related peripheral section Programmers must follow the manual s suggested procedures of initialization or access Programmers must understand their target hardware operation and access the peripherals accordingly i It may be necessary to set the port data register before setting the direction register If otherwise the default output High may cause fault triggering ii It may be necessary to access the port data register in byte form instead of bit If otherwise the control or monitoring events may not be synchronized Programmers should read up any Technical Update or revised items of User manual to obtain
25. v 1 00 March 2004 Page 20 of 21 PRELIMINARY tENESAS T Embedded C Programming II ECProgramll 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 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
26. xternal function which is located in the external memory 0x06000000 ii Function pointer with passing parameters typedef void extFnPtr char char define EXT_ADDR_PTR 0x0600000 define EXT_FN_PTR_ADDR unsigned long EXT_ADDR_PTR define EXT_FN extFnPtr EXT_FN_PTR_ADDR char p char var EXT_FN p var AN0403001 Rev 1 00 March 2004 Page 18 of 21 PRELIMINARY tENESAS sete Embedded C Programming II ECProgramll 4 Conclusion The emphasis of this document is to illustrate the ports peripherals and external memory access methodology It also creates the awareness of the basic hardware knowledge needed for firmware programming Reference H8 38024 Hardware User Manual Renesas 8 3048 Hardware User Manual Renesas HEW C C Compiler Assembler Optimizing Linkage Editor manual Renesas A book on C by Al Kelley Ira Pohl Addison Wesley The Practice of Programming by Brain W Kernighan amp Rob Pike Addison Wesley Fundamentals of Embedded Software where C and Assembly Meet by Daniel W Lewis Prentice Hall Programming Embedded Systems in C and C by Michael Barr O REILLY Writing Solid Code by Steve Maguire Microsoft Press AN0403001 Rev 1 00 March 2004 Page 19 of 21 PRELIMINARY l HEW E EN ESAS Embedded C Programming II ECProgramll Revision Record Description Rev Date Page Summary 1 00 March 2004 First edition issued AN0403001 Re
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