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SC51 User`s Manual

1. float exp float x Related Functions float frexp float value int eptr float ldexp float value int exp float log float x float log10 float x float pow float x float y float sqrt float x Prototype in math h Remarks exp calculates the exponential function e SC51 User s manual 43 http www spjsystems com frexp calculates the mantissa x a float less than 1 and n an integer such that value x 2 frexp stores n in the integer that eptr points to Idexp calculates value 2 log calculates natural logarithm of x log10 calculates the base 10 logarithm of x pow calculates x sqrt calculates Vx Return value All these functions on success return the value they calculated exp returns e frexp returns x lt 1 where value x 2 Idexp returns value 27 log returns natural logarithm of x log10 returns the base 10 logarithm of x pow returns x sqrt returns Vx Function rounds down Syntax float floor float value Prototype in math h Return value floor finds the largest integer not greater than x It returns this integer as a float value See also ceil Function Calculates x modulo y the remainder of x y Syntax float fmod float x float y Related functions float modf float x float ipart Prototype in math h Remarks fmod calculates x modulo y the remainder f where x iy f for some integer
2. SC51 User s manual 24 http www spjsystems com e Interrupt functions must end with a RETI instruction rather than RET instruction e At the beginning of interrupt functions important registers such as accumulator or flags must be saved and these must be restored just before the end of interrupt function It is also usual to change register bank In case of SC51 programs all non interrupt functions use register bank0 One another register bank must be reserved for each priority level of interrupts Due to the above differences it is necessary to use somewhat different syntax to declare an interrupt function interrupt INTR NUM FuncName using N where interrupt is a keyword that informs the compiler that this is an interrupt function rather than ordinary function INTR NUM can be a constant in the range 1 to 32 which identifies the interrupt number and consequently the vector location associated with it The vector location address associated is INTR_NUM 1 8 3 Thus INTR_NUM 1 corresponds to External Interrupt0 EXTO whose vector address is 0003H INTR_NUM 2 corresponds to Timer0 TO interrupt whose vector address is 000BH Symbolic constants such as INT EXTO INT TMRO are defined in the file STANDARD H We strongly recommend that you should include lt standard h gt in your program and use the appropriate symbolic constant as INTR_NUM FuncName is the name of the interrupt function
3. char type or unsigned char type gets the lowest priority However the compiler behaves differently for some operators i e z j amp n c For these operators the result is to be written back onto the left hand side operand which must be a variable Hence the compiler will ALWAYS convert the right hand side operand into the type of left hand side operand e g if you write x f where x is of type int and f is of type float then compiler will generate code to convert the value of f into integer and then multiply the value of x by it and finally store the result which will be naturally int type back into the variable x ole 3 6 Constants Integer constants may be written in decimal form e g 123 or 30945 or in hexadecimal form with Ox prefix e g Oxff Character constants must be enclosed in single quotation marks e g A or String constants must be enclosed in double quotation marks e g This is a string constant Floating point constants are always considered to be of type float Also floating point constants must be written with a decimal point otherwise they may be considered as integer constants e g 123 will be considered as the integer value 123 whereas 123 0 will be considered as the floating point value 123 The suffix L can be attached to a constant to force it to long int type For example 123L is the long int value 123 Without
4. int par2 long int par3 SC51 User s manual 16 http www spjsystems com some statements here sy this is not a valid function definition 3 9 Compiler control lines include directive may be used to include another file However nesting of include files is not allowed i e if file2 is included in filel then there may not be any include statement in file2 The syntax is include lt file_name gt or include file_name If the file name is enclosed in lt gt then that file will be looked for in the folder INC in the path where SC51 is installed If file_name is enclosed in then it will be looked for in the current folder define and undef directives may be used to define or undefine a macro A macro may or may not have parameters e g define max_output 2048 This statement defines the symbol max_output to the value 2048 i e wherever you write the word max_output it will be replaced by 2048 by the pre processor before compiling A macro with parameters can be defined as define product x y x y Here x and y are parameters While using the macro you can substitute the x and y with anything else e g if you write value product factor 123 45 it will be replaced by value factor 123 45 SC51 User s manual 17 http www spjsystems com tifdef ifndef else and endif directives may be used for conditional compiling The syntax is
5. it must follow the usual rules for identifier name using is the keyword required to specify the register bank to be used for this interrupt function N is the register bank number to be used for this interrupt function It is legal to specify any value in the range 0 to 3 here However it is strongly recommended to use only values 1 to 3 because register bank is used by all non interrupt functions hence interrupt function must not use it If incorrect register bank is specified the entire program may malfunction The SC51 compiler treats an interrupt function differently than ordinary functions e The SC51 compiler will automatically insert a jump instruction at the vector location which points to this interrupt function e At the beginning of interrupt function the compiler automatically generates code to save important context for example accumulator flags and so on write your code here SC51 User s manual 25 http www spjsystems com 3 10 9 The compiler also generates instruction to switch register bank to the specified value e At the end of interrupt function the compiler automatically generates code to restore the saved context and switch back to original register bank e The compiler uses RETI instruction rather than RET to terminate the interrupt function Please note an interrupt function can not have any parameters Absolute Register Addressing The SC51 compiler generates Asse
6. Syntax finclude lt macros31 h gt start timer0 Prototype in macros31 h Remarks Sets bit 4 of TCON to start timer0 Return value None See also stop timer0 Function Starts timer 1 Syntax finclude lt macros31 h gt start timerl 5 Prototype in macros31 h Remarks Sets bit 6 of TCON to start timerl Return value None See also stop timerl SC51 User s manual 68 http www spjsystems com stop_timer0 Function Stops timer 0 Syntax finclude lt macros31 h gt stop_timero Prototype in macros31 h Remarks Clears bit 4 of TCON to stop timer0 Return value None See also start_timer0 Function Stops timer 1 Syntax finclude lt macros31 h gt stop timerl Prototype in macros31 h Remarks Clears bit 6 of TCON to stop timerl Return value None See also start timerl Function Appends one string to another Syntax char strcat char dest char src Prototype in string h Remarks strcat appends a copy of src to the end of dest The length of the resulting string is strlen dest strlen src Return value strcat returns a pointer to the concatenated strings SC51 User s manual 69 http www spjsystems com strcmp Function Compares one string to another Syntax int stremp char sl char s2 Prototype in string h Remarks strcmp performs an unsigned comparison of sl to s2 starting with the first character in each string and continui
7. low byte of parl is pushed mov a r3 push acc high byte of parl is pushed lcall some func MOV a Sp clir subb a 3 decrement sp by total no of mov sp a bytes required for ALL parameters For more information about assembler language programming please refer to the user s manual of SASM51 assembler SASMS51 PDF SC51 User s manual 78 http www spjsystems com Appendix A Error and Warning messages This appendix describes all warning and error messages produced by the compiler The description includes possible causes and remedy or suggestion An Error message is produced by the compiler when the severity of the error makes it impossible for the compiler to produce the assembly language or machine code output Thus if you encounter an error message while compiling it indicates that the compiler is unable to produce the ROMable code file BIN On the other hand a Warning message is produced by the compiler when it does not know whether it really is an error or not It is expected that the programmer should decide it himself and hence the compiler also prints sufficient information in the warning message However even if you encounter one or more warning messages the compiler still completes the compile process and produces the ROMable code file provided there are no Errors The programmer may then analyze each warning message and then only decide whether to use the compiler output or to make changes in the
8. Function Enables INTO external interrupt Syntax include lt macros31 h gt enable_ex0 Prototype in macros31 h Remarks Sets bit 0 of IE so that external interrupt INTO gets enabled Return value None See also disable_ex0 Function Enables INT1 external interrupt Syntax finclude lt macros31 h gt enable ex1 Prototype in macros31 h Remarks Sets bit 2 of IE so that external interrupt INT1 gets enabled Return value None See also disable exl Function Enables receiver of serial port Syntax finclude lt macros31 h gt enable rx Prototype in macros31 h Remarks Sets bit 4 of SCON so that serial port s receiver gets enabled Return value None See also disable rx SC51 User s manual 40 http www spjsystems com enable ser Function Enables serial port interrupt Syntax include lt macros31 h gt enable ser Prototype in macros31 h Remarks Sets bit 4 of IE so that serial port interrupt gets enabled Return value None See also disable ser Function Enables timer 0 interrupt Syntax include lt macros31 h gt enable tO Prototype in macros31 h Remarks Sets bit 1 of IE so that Timer O interrupt gets enabled Return value None See also disable_t0 Function Enables timer 1 interrupt Syntax include lt macros31 h gt enable t1 Prototype in macros31 h Remarks Sets bit 3 of IE so that Timer 1 interrupt gets enabled Return value None
9. Prototype in stdio h Remarks Waits till a character is available from the standard input device which is on chip serial port of 8051 When a character is available reads it This function is called by scanf function to get input Return value Returns the character read from standard input device See also scanf getchare Function Reads acharacter from standard input device Syntax include lt standard h gt char getchare Prototype in stdio h Remarks Waits till a character is available from the standard input device which is on chip serial port of 8051 When a character is available reads it and also echoes it back to the standard output device which is again on chip serial port of 8051 unless the user redirects it by writing his own putchar function Return value Returns the character read from standard input device See also scanf getchar Function Puts the CPU in idle mode Syntax include lt macros31 h gt go_idle Prototype in macros31 h SC51 User s manual 46 http www spjsystems com Remarks Sets bit 0 of PCON so that the CPU goes to idle mode in which it consumes less power Return value None See also powerdown Function Separates the high order nibble Syntax unsigned char hi nibb unsigned char ch Prototype in standard h Return value Returns the high order nibble of ch See also lo_nibb Function Initializes the on chip serial port Syntax void init_lc
10. ifdef symbol_name set of statements 1 telse set of statements 2 endif If symbol name is a defined macro name then the ifdef expression evaluates to true and the set of statements 1 will be compiled Otherwise the set of statements 2 will be compiled The else and set of statements 2 is optional The ifndef expression evaluates to true if symbol name is not defined Rest of the syntax is same as that for ifdef 3 10 Additional features 3 10 1 Using Special Function Registers SFR You can access the SFRs of the micro controller by using the SFR declaration SFR is an additional keyword It allows you to define a SFR The syntax is SFR sfr_name sfr_addr where sfr_name is the name of the SFR you want to define e g TMOD and sfr addr is it s address e g 0x89 There is no need to write a semicolon after a SFR declaration Thus the statement SFR TMOD 0x89 defines the SFR TMOD with an address 89 Hex Once a SFR is declared you can use it in your C program as if it were a variable of type unsigned char e g you may write TMOD 0x11 This statement will generate code to write the value 11 Hex in TMOD In fact we have already declared most of the SFRs for you in different header files e g the file SFR31 H contains the declarations for all 8031 8051 8751 SFRs If you include the file SFR31 H in your C program you can use all 8031 SFRs as variables of unsigned char type Similarly there are oth
11. 9 http www spjsystems com 2 Installation The SC51 software CD includes an automatic installation program called SETUP EXE Insert the SC51 software CD in your CD ROM drive and run SETUP EXE from the CD This will start the installation and the setup program will ask you some questions e g where do you want to install the software in the default path or somewhere else Please supply the answers to all the questions and complete installation Please read this manual carefully before you start using the software SC51 User s manual 10 http www spjsystems com 3 Language Reference This chapter describes the general syntax rules for the C language as implemented by this compiler In order to keep your programs portable we have tried to stick to ANSI standard C as far as possible However we have added certain extentions to ANSI C in our compiler especially to take advantage of the special features of 8051 architecture such as bit addressing capability In this implementation of C Compiler there are also some minor variations and limitations in many cases these are due to the limitations of 8051 architecture This chapter provides information about such additional features Please also read the appendix Limitations of the compiler which lists certain limitations of this C compiler and some known bugs Please note that this is NOT an authoritative document describing the C language in general Many books from reputed pu
12. C file name You may not use ORG statement in assembly language patch file If you must use the ORG statement e g to ljmp to ISR use these at the end of the assembly language file You can access global variables declared in C program from assembly language e g if varl is declared as global variable in C program then you can use the symbol _varl as the address of that variable i e you must attach an underscore _ to the left of the variable name Please note that all variables reside in external data memory in case of large model unless memory area specifier or notation is used On the contrary all variables reside in internal RAM in case of small model unless memory area specifier or notation is used 3 10 3 The asm keyword This is an additional keyword which allows you to insert assembly language statements directly into your C program This keyword when used must appear as the first word of a line Everything following this keyword up to the end of line is directly copied into the ASM output file Please note that no syntax checking is done by the compiler on this assembly language statement it is done later on by the assembler SC51 User s manual 19 http www spjsystems com 3 10 4 The BIT keyword The BIT keyword is an additional non ANSI keyword It can be used to define pseudo variables of bit type e g suppose you are using bit 0 of P1 for some purpose say to switch on a motor Then you mi
13. Return value cos returns the cosine of x See also acos Function Returns the hyperbolic cosine of the argument SC51 User s manual 34 http www spjsystems com Syntax include lt math h gt float cosh float x Prototype in math h Remarks This function is NOT included in the library but it is given in the form of source code It s source code can be found in SOURCE CFILES MATH C Return value cosh returns the hyperbolic cosine of x See also cos Function Produces a delay Syntax include lt standard h gt void delay int count Prototype in standard h Remarks Produces a certain delay Since the crystal frequency in the target system is not known this function passes count number of clock cycles only Thus if you are using 8031 with 12 MHz crystal you may say that this function produces a delay of count micro seconds where count is the integer parameter you pass to it However if you are using a different crystal frequency and or different CPU it may not be so The accuracy of this function is plus or minus 50 cycles i e if you call delay function with count parameter 20000 then it will return after n clock cycles where n will be gt 19050 and lt 20050 Also please note that this functions produces a software delay Thus if interrupts are enabled then this function may produce more delay than is expected Because if interrupt occurs during this function then it will take some more time
14. See also disable t SC51 User s manual 41 http www spjsystems com enable t2 Function Enables timer 2 interrupt Syntax include lt macros31 h gt enable t2 Prototype in macros31 h Remarks Sets bit 5 of IE so that Timer 2 interrupt gets enabled Return value None See also disable t2 Function Makes INTO edge sensitive Syntax include lt macros31 h gt ex0_edge Prototype in macros31 h Remarks Sets bit 0 of TCON so that external interrupt INTO becomes edge sensitive Return value None See also ex0 level Function Makes INTO level sensitive Syntax include lt macros31 h gt ex0_level Prototype in macros31 h Remarks Clears bit 0 of TCON so that external interrupt INTO becomes level sensitive Return value None See also ex0 edge SC51 User s manual 42 http www spjsystems com exl edge Function Makes INT1 edge sensitive Syntax include lt macros31 h gt exl_edge Prototype in macros31 h Remarks Sets bit 2 of TCON so that external interrupt INT1 becomes edge sensitive Return value None See also exl1 level Function Makes INT1 level sensitive Syntax include lt macros31 h gt exl_ level Prototype in macros31 h Remarks Clears bit 2 of TCON so that external interrupt INT1 becomes level sensitive Return value None See also exl_edge Function exponential function Syntax finclude lt math h gt
15. a few exceptions like the SFR statement or the BIT statement etc If you forget to write the semicolon you will see this error message SC51 User s manual 81 http www spjsystems com Misplaced continue The continue keyword must be used inside a loop e g in a for loop or a do while loop or in a while loop However when the compiler encounters a continue statement which is NOT inside the body of a loop it will print this error message Misplaced else The else keyword must be used in conjunction with the if keyword Use of else keyword without a corresponding if will produce this error Misplaced break The break keyword must be used inside a loop e g in a for loop or a do while loop or in a while loop or inside a switch statement However when the compiler encounters a break statement which is NOT inside the body of a loop or a switch statement it will print this error message do statement missing while The do keyword must have a corresponding while at the end of the do while loop If the while keyword is missing this error message is printed case outside of switch The case keyword must be used inside a switch statement However when the compiler encounters a case statement which is NOT inside a switch statement it will print this error message Colon Missing Th
16. all or most of your data in 128 bytes of RAM itis advisable to compile your program using small model If you need more data variables however you can either use large memory model or use the memory area specifiers to force some variables in idata xdata or pdata area Wherever possible use unsigned char data type instead of int e g the count variable in a for loop etc If the count does not exceed 255 you may use unsigned char type variable instead of int Since the 8051 has instructions only to manipulate 8 bit data and bits it is easier to handle 8 bit data elements rather than 16 bit or 32 bits For the same reason use of S suffix on constants can produce smaller code As an example consider the statement x y 7 where x and y are unsigned char variables The constant 7 is considered as an int constant 0007H Due to ANSI C integer promotion rules the single byte unsigned char value of y is converted to a two byte int value by appending a byte OOH to it s left side After that code is generated to perform multiplication of two 16 bit numbers The 8051 does not provide any instruction for 16 bit multiplication which means the compiler must call a library sub routine or generate lot of in line code Did you really expect all that big code In most cases no If you really expected a single byte multiplication then you should use the S suffix on 7 In other words re write the above statement a
17. bcd2int converts the unpacked BCD string str into an integer number It considers the first ndigits digits of str Return value bcd2int returns the integer value See also int2bcd Function Rounds up Syntax include lt math h gt float ceil float x Prototype in math h Return value ceil returns the smallest integer greater that or equal to x See also floor Function Clears double baud rate Syntax include lt macros31 h gt clr double baud Prototype in macros31 h Remarks Clears bit 7 of PCON so that baud rate is not doubled Return value None See also set_double_baud Function Clears receiver interrupt SC51 User s manual 33 http www spjsystems com Syntax include lt macros31 h gt clr BIO 3 Prototype in macros31 h Remarks Clears RI bit in SCON so that serial port s pending receiver interrupt is cleared Return value None See also clr_ti Function Clears transmitter interrupt Syntax include lt macros31 h gt clr_ti Prototype in macros31 h Remarks Clears TI bit in SCON so that serial port s pending transmitter interrupt is cleared Return value None See also clr ri Function Returns the arc cosine of the argument Syntax include lt math h gt float cos float x Prototype in math h Remarks This function is NOT included in the library but it is given in the form of source code It s source code can be found in SOURCE CFILES MATH C
18. constant string then you can write the string on multiple lines e g char arr 100 hello world Please note the backslash at the end of first line It indicates that string is continued on next line 2 While passing parameters to a function the compiler checks only first 12 parameters for type conversion 3 Type casting is not supported 4 Sometimes the compiler does not recognize the unary minus operator correctly It is recommended to use the expression 0 something instead of just writing something e g x 10 may produce error x 0 10 will not produce error x z 15 may produce error x 0 z 15 will not produce error 5 Maximum 2 dimensional arrays are supported Arrays with more than 2 dimensions are not supported 6 Pointer to pointer is not supported 7 Array of pointers is not supported 8 A member of a struct union may not be a pointer 9 A member of a struct union may not be a struct union SC51 User s manual 86 http www spjsystems com Appendix C 10 ways to improve code efficiency This appendix lists some useful suggestions in order to use the compiler in a better and more efficient way 1 2 3 4 5 Small model produces smaller code because all or most variables reside in internal RAM data memory area Manipulating internal RAM is much easier than external RAM So if you are able to fit
19. function to read one character from some other device then scanf takes all it s input from this new device The sscanf function reads the input from the first argument src The format string The format string present in both scanf and sscanf controls how each function will scan convert and store it s input fields There must be enough address arguments for the given format specifications if not the results are unpredictable and likely to disturb the entire system Excess address arguments more than required by the format are ignored The format string contains format specifications which direct it to read and convert characters from the input field into specific types of values and store them in the locations given by the address arguments The format specifications have the following form o 1 type character Each format specification begins with a percent character After the percent character there may be an optional type modifier character i e 1 followed by mandatory type_character The following table lists valid type characters the type of input expected by each and in what format the input will be stored Type Input Type of argument Character decimal integer pointer to int int arg decimal integer pointer to int int arg u decimal integer pointer to int int arg E floating point float pointer to float float arg character char pointer to character char arg SC51 User
20. identifier names break case char continue default do double else void float for goto LE int interrupt long return short SC51 User s manual 12 http www spjsystems com unsigned asm struct union sizeof SFR bit BIT data idata bdata xdata pdata code using extern Although double and sizeof are not supported in this version still these are reserved keyword because these may be supported in later versions 3 4 Data types The following table lists all the data types which are supported by this C compiler their range of possible values and their size in bits unsigned char 8 0t0255 ehar 8 _ P8to17 Git 16 E to 32767 TT SC51 User s manual 13 http www spjsystems com Apart from these basic data types you can declare one dimensional arrays of any of these types except the bit type There are some more restrictions on the use of bit data type as follows e You can not declare arrays of bit type variables e bit type variables can not be passed as parameters e A bit type variable must be a global variable It can not be declared as a local variable or a parameter e There can be maximum 120 variables of bit type in any program e bit type variables always reside in Internal RAM bit addressable memory area 0x20 to 0x2f regardless of which memory model you are using e While assigning a constant value to any bit variable you can assign only one of the two possi
21. in a great amount of saving in code size and also the clock cycles required However using outportb and inportb functions is also perfectly legal By using this feature you can declare variables at any location in internal or external RAM Thus even if you are using small memory model still you can forcefully keep some variables in external RAM at any address Also even if you are using large memory model you can forcefully keep some variables in internal RAM at any address However the compiler does NOT check whether the specified address is used by some other variable or temporary variable or stack or registers Thus it is the PROGRAMMER s RESPONSIBILITY to specify a valid address which is not used for any other purpose interrupt functions and the using directive The SC51 compiler supports a special type of functions interrupt functions As the name implies these are Interrupt Service Routines ISRs They are different from ordinary functions in many respects e Interrupt functions are not called by user program but are automatically invoked by hardware when the corresponding interrupt event occurs As a result interrupt functions must not have any parameters e For the same reason interrupt functions can not return a value e All interrupt functions are associated with a vector location A jump instruction must be placed at the vector location such that it will transfer control to the interrupt function
22. in the library but it is given in the form of source code It s source code can be found in SOURCE CFILES MATH C Return value asin returns the arc sine of x See also sin SC51 User s manual 31 http www spjsystems com Function Converts ASCII string to floating point number Syntax finclude lt stdlib h gt float atof char str Prototype in stdlib h Remarks atof converts the ASCII string str into a floating point number Return value atof returns the converted floating point value If the string can not be converted returns 0 See also atol atoi Function Converts ASCII string to integer number Syntax finclude lt stdlib h gt int atoi char str Prototype in stdlib h Remarks atoi converts the ASCII string str into a integer number Return value atoi returns the converted integer value If the string can not be converted returns 0 See also atol atof Function Converts ASCII string to long integer number Syntax include lt stdlib h gt long int atol char str Prototype in stdlib h Remarks atol converts the ASCII string str into a long integer number Return value atol returns the long integer value If the string can not be converted returns 0 See also atoi atof SC51 User s manual 32 http www spjsystems com bed2int Function Converts BCD string to integer number Syntax include lt etc h gt int bed2int char str 10 int ndigits Prototype in etc h Remarks
23. myacc and the MSByte should be written at myacc 1 Please note that if a function s return value is of type bit then you should use the bit location bit_acc instead of internal RAM location myacc e g if you want to return 1 bit type then you must write setb bit acc ret at the end of the function 5 3 Assembly Language Functions with parameters If you want the assembly language function to take parameters you must start and end the function in a specific manner 5 3 1 Accessing parameters in assembler program At the beginning You must write these two lines push bp mov bp sp At the end you must write these three lines mov sp bp pop bp ret It is also necessary to declare bp as an external symbol with the declaration EXTRN DATA bp When a function is called from C language program it s parameters are pushed onto stack The first parameter is pushed first To access these parameters you should make use of bp For example consider this C language statement some_funcl parl par2 SC51 User s manual 76 http www spjsystems com Let us assume that parl is of int type and par2 is of unsigned char type The last byte of the first parameter can be always found at the address bp 3 e g to load the value of parl in R3 R2 you may write mov a bp ede Cc subb a 4 mov r0 a RO bp 4 addr of parl mov a r0 read LSByte of parl mov r2 a p
24. width is affected Specifier n n characters are always printed If the output value has less than n characters the output is padded with blank If the output value has more than n characters then it is truncated not rounded to first n characters only On n characters are always printed If the output value has less than n characters the output is padded with zero If the output value has more than n characters then it is truncated not rounded to first n characters only However please note that in this implementation of the compiler the maximum allowed value of the width specifier is 10 SC51 User s manual 56 http www spjsystems com How the precision specifier affects the output The precision specifier affects the output of only floating point values It determines how many digits will be printed after the decimal point If the precision is not specified at all then a floating point value will be printed with 3 digits after the decimal point If the precision is specified as n then n digits will be printed after the decimal point If the output value has more than n digits after the decimal point then the output will be truncated NOT rounded If it has less than n digits then the output is padded with 0 However please note that in this implementation of the compiler the maximum allowed value of the precision specifier is 6 The optional input size modifier 1 or b applies only if the type character is d o
25. will be printed Too big macro definition If a macro definition is too big to fit in the available memory this error message will be printed Please note that multi line macro definitions are not supported in this version of the compiler Syntax error in include statement or file not found If the include statement is not correctly written or if the compiler is unable to open the included file this error message will be printed Macro has too many parameters A macro can not have more than 10 parameters If you attempt to define a macro with more than 10 parameters this error message will be printed Invalid Statement If an invalid preprocessor directive is encountered this error message will be printed Line Too Long Any line in your program must not have more than 240 characters If a line is found to have more than 240 characters this error message will be printed Too many ifs The ifdef or ifndef statements can be nested However this version of the compiler does not support a nesting level of more than 10 If you attempt to nest more than 10 ifdef or ifndef statements this error message will be printed SC51 User s manual 84 http www spjsystems com Too many gt 128 SFR declarations Using the SFR keyword you can define Special Function Registers to be used as pseudo variables However you may not declare more than 128 SFRs If you attempt to do so this error message will be printe
26. 31 h Remarks Clears bit 4 of IE so that serial port interrupt remains disabled Return value None See also enable ser Function Disables timer 0 interrupt Syntax include lt macros31 h gt disable t0 Prototype in macros31 h Remarks Clears bit 1 of IE so that Timer 0 interrupt remains disabled Return value None See also enable_t0 Function Disables timer interrupt Syntax include lt macros31 h gt disable t1 Prototype in macros31 h Remarks Clears bit 3 of IE so that Timer 1 interrupt remains disabled Return value None See also enable_tl SC51 User s manual 38 http www spjsystems com Function Disables timer 2 interrupt Syntax include lt macros31 h gt disable t2 Prototype in macros31 h Remarks Clears bit 5 of IE so that Timer 2 interrupt remains disabled Return value None See also enable_t2 Function Enables interrupts Syntax include lt macros31 h gt enable Prototype in macros31 h Remarks Sets only bit 7 of IE so that all interrupts may be enabled Return value None See also enable_all disable Function Enables interrupts Syntax include lt macros31 h gt enable_all Prototype in macros31 h Remarks Sets all bits of IE so that all interrupts are enabled Please note the subtle difference between enable and enable_all Return value None See also enable disable_all SC51 User s manual 39 http www spjsystems com
27. 31 h Remarks Sets bit 1 of IP so that timer O interrupt gets a high priority Return value None See also set lo 0 SC51 User s manual 62 http www spjsystems com set hi tl Function Sets high priority for timer 1 interrupt Syntax finclude lt macros31 h gt set hi t1 Prototype in macros31 h Remarks Sets bit 3 of IP so that timer 1 interrupt gets a high priority Return value None See also set_lo_tl Function Sets high priority for timer 2 interrupt Syntax include lt macros31 h gt set hi t2 s Prototype in macros31 h Remarks Sets bit 5 of IP so that timer 2 interrupt gets a high priority Return value None See also set_lo_t2 Function Sets low priority for INTO Syntax include lt macros31 h gt set lo ex0 Prototype in macros31 h Remarks Clears bit O of IP so that external interrupt INTO is gets a low priority Return value None See also set hi ex0 SC51 User s manual 63 http www spjsystems com set lo exl Function Sets low priority for INT1 Syntax finclude lt macros31 h gt set lo ex1 A Prototype in macros31 h Remarks Clears bit 2 of IP so that external interrupt INT1 is gets a low priority Return value None See also set_hi_ex1 Function Sets low priority for serial port interrupt Syntax include lt macros31 h gt set_lo_ser gt Prototype in macros31 h Remarks Clears bit 4 of IP so that serial port interrupt gets a low priority Return
28. 31 h gt set_com_mode mode sm2 ren 2 Prototype in macros31 h Remarks This macro writes sets and or clears appropriate bits in SCON In effect it sets the serial port in the given mode it sets the SM2 bit to sm2 and if ren is 1 it enables the receiver Return value None Function Sets double baud rate Syntax finclude lt macros31 h gt set double baud 5 Prototype in macros31 h Remarks Sets bit 7 of PCON so that baud rate is doubled Return value None See also clr double baud Function Sets high priority for INTO Syntax include lt macros31 h gt set hi ex0 s Prototype in macros31 h Remarks Sets bit O of IP so that external interrupt INTO is gets a high priority Return value None See also set lo ex0 SC51 User s manual 61 http www spjsystems com set hi exl Function Sets high priority for INT1 Syntax finclude lt macros31 h gt set hi ex1 A Prototype in macros31 h Remarks Sets bit 2 of IP so that external interrupt INT1 is gets a high priority Return value None See also set_lo_ex1 Function Sets high priority for serial port interrupt Syntax finclude lt macros31 h gt set hi ser i Prototype in macros31 h Remarks Sets bit 4 of IP so that serial port interrupt gets a high priority Return value None See also set lo ser Function Sets high priority for timer 0 interrupt Syntax finclude lt macros31 h gt set hi tO A Prototype in macros
29. AREGS this point onwards absolute register addressing will be enabled By default absolute register addressing is enabled SC51 User s manual 26 http www spjsystems com 4 SC51 Library Functions Reference List of functions in alphabetical order 1 abs 2 acos 3 asin 4 atof 5 atoi 6 atol 7 bcd2int 8 ceil 9 clr_double_baud 10 clr_ri 11 clr ti 12 cos 13 cosh 14 delay 15 delay ms 16 disable 17 disable all 18 disable ex0 19 disable_ex1 20 disable_rx 21 disable ser 22 disable_t0 23 disable tl 24 disable t2 25 disp_Icd 26 enable 27 enable all 28 enable ex0 29 enable exl 30 enable rx 31 enable ser 32 enable to 33 enable tl SC51 User s manual 27 http www spjsystems com 34 enable t2 35 ex0 edge 36 ex0 level 37 ex1 edge 38 ex 1 level 39 exp 40 floor 41 fmod 42 frexp 43 getbyte 44 getch 45 getchar 46 getchare 47 go_idle 48 hi_nibb 49 init_ser 50 inportb 51 int2bcd 52 isalnum 53 isalpha 54 isascii 55 isdigit 56 islower 57 isspace 58 isupper 59 isxdigit 60 itoa_c31 61 labs 62 ldexp 63 log 64 log10 65 long2bcd 66 lo_nibb 67 Itoa_c31 68 memset 69 modf 70 movmem 71 outportb 72 peekb 73 pokeb SC51 User s manual 28 http www spjsystems com 74 pow 75 powerdown 76 printf 77 putchar 78 puts 79 scanf 80 sendbyte 81 ser rdy 82 set com mode 83 set double baud 84 se
30. E EE ER ROL Beas et EE HE NE oat 42 CXO NOVEL EER AE DR EE SR GE EB ER ele a EE T ee neh EE 42 ER EE EO N EE BE EE N 43 OND level ER sai O EG ES Ee ee oN bv Cohiba SEE 43 AE EE OT EL N OE OR AE cecal EA AE 43 oa EER a ad Te EL RA EE N eta 44 TRO a EE EE LO OR AA EE LEO DE HO dd VAA I AAA RE EA ED JOSE SEES EE N EE EE 45 AE ik hea AE ME EE OE EE AE AE 45 AR EE EE E SERENE 45 betehat hata O O tata Ge AG es ed BESET 46 OT CDI AO EE EE EE DR EE Mong acta 46 BOE MS N EE N Ge ee ES SEE ee god ee De ie ee 46 RE Babess EE EE N A EN 47 MESS EE EE N AE EE EE HE N 47 EA Oe MEE OE TR EO RE ag ld 47 IJ P DC case dato RE N EERIE EEE Sv Pe REE OR Bil 48 FRY 711711 ET RE HE IE ee eae OR 48 SC51 User s manual 4 http www spjsystems com OE N RE EO ER RE EN 48 KAREE AE ER EE EET REE 0 OEE RR ii 49 EE EE E AE EE EE EE EE OE LR ENG 49 YE OE EE OE N AO EE N OE bade 49 ISRAEL GES SON Se EE Dds SB ke EE NE BE E ES 49 IS UPRER Da ae lorca Ee DE 50 PSL GUE OE RE ON EO N Ee tart EE ee OP 50 Ad EE EE EA ER N 50 NO Oe REPO ECE Pan ROPER GREG A EO IE EG 51 ET IE EE E ED OE N EIDE TEE SED EGE Ed 51 VOD A EE OE dae aa 51 VOL TO EE DE A a O A A De e a 51 ION 22 bed re DE EE Me DE Do AE 52 LOAN ERR GE EE EE ER A O NE EDT FR EE EE PN 52 N AT RE DE EE OO N 52 KAR MEE TE RE MR DR EE EE ED 53 ie RE EE ie NE EE EE OE Ed De Oe EE de N 53 AG EE EE N EE Ed ED ere 53 AE RG EE A ER RE EE EN 93 Ya SR N e AO EE E EE SUE 54 pokeb A A O IS 54 ie SEE OE AE EE AT OE ME DE E
31. E Ek ee 54 DEE OWEN De AA A Ge Ge ee Me Ge 55 EE OT OE ER ER cae ae EE HO J3 BEE ee oes ee ve Ge GER Dee ai se EE DE De on O in GR ee ek 57 jy EED A AN EE EN OE il dR 58 YA AE RE EE OE E EE IE NE EE ERE RUTEN SE 58 SCT LC MM EN HO OR ER N OE Rectal 60 STA IS EE A RE IE EE EE 60 set com ode ER A ER Ee GE ee ee Ee GE se ee 61 SCL AOUDIC DOUG HE SE SE ee ee AAA A ED sele Pe ee Ds ee ed es 6l YAE EA EE EE OR EE 6l ASA AE AE HE ER OR ENS REG 62 AE IM EE RE NE OR EL N EE 62 set hi tO este EE EL O RE ee N Ee ie 62 AA EE EE EE N EE sibel wane Ea beck 63 SEENE AN EE OE EA A 63 AE AAR OE ET OE OR KIE OO OE 63 ds a ER RE EE EE 64 SER EN A E KERE E GE EE eN GE hi DE ee AE 64 SC51 User s manual 5 http www spjsystems com sel MO TO ke DE ee ae EE N Se AE RE SENSE ee ER ee ie n ee TE 64 YAE ME S ER RE ES R EEA Ee GE EE OA OEE EA ER EEE EEA AEA 65 ARE OR EE ME OR EE OE EE 65 YE ME SO EE EE ER OE OE ab ea tenses 65 selet l mode ER ESE ad ATA E EA Bobs EDE Pid ES Bel NEE ED s 66 A A N ee ee ED ee ee OO 66 RE OE EE EE OE IE LES 66 AE EA OE RE EE MA 67 ad AE EE ER AE RE NE ER AE AN EE 67 EE EE MOLL EE DE IN 67 YES A RE RE N N OE 66 GE ER EE OR EE N EO OE OR EE OE N 66 SEAMOS EO ER ERGE De Ee Re Ee EE PN eo ee 66 MODE TUVO LA ER EE OE N AN EE RR OR oe 69 STOP OE ME N EO ts OE OE EE oatid 69 EC OE RE N DR EE HERE EE EE 69 EE N DE EER Ee EE EO EO Ad RE hades denis 70 Se CD EE EE EE BAR EE DEAR nautical 70 AE AE EE ER AA IE EE ME EE 70 EE dina 71 STI
32. ETA ed 80 Redeclaration of identifier OR function gt sis Ese Es N oe ke Ee ek Ee de Ed ve KG Ne ie 80 T00 M ny ldentifers AS A O Ge Ve EG ge 60 Unknown Identifier Seeds ee GE ee ER sg E a Ee ee ain ele as 60 Tiv ad EIE EE EG Ge AE A DAA A Aa SI Too many errors DIA AA OE RA ALE Ee ANE SEAL ee ei Eta 81 Invalid Statement ibas SI Syntax error A AS EO OO OE N a cda SI Misimate Boe ker sa ne ci 81 TOO Man E 111A A A EEEE A A E N Ge SI Statement MESS E Wese ee see oe bee it Ra oe eu es bo ee EE tdo SI Misplaced continue Scr sais AE ti 82 Misplaced els runnar loci 82 Misplaced break on Rees A e aie lisa e a aT ia 82 do statement missing Wild 82 case outside OF SWITCH atada die 82 Colon Missing AA A GE DE ad lei IE IOS Ries ila OR Lil 82 Too Many Default Statements OR default May be Outside of switch 82 Type MS IA ES A RR eb A A OR Ee ee Ge 83 Too many goto statements max 10 A EE es aaa 83 Undefined label eed enda teen ede sk Ee ri en ie oes ee GE ee Gee 83 Unde fined MACTO SS A A Ge GE tad 83 Macro Parameters OE OER EE N OE cid 83 Too many few parameters passed tO MACTO esse se ee ER ee ee RA ee Ee Re ee Ee Re 83 Macro definition Syntax error He sees oes da 83 Unexpected else or endif sd RS e Ee 84 Too many ea ea Ne Oe N N EE AAA N Ed 84 Too big macro definitii Es SEE nh aie naa ESE N al 84 Syntax error in include statement or file not found esse ee ee ee RR ee 84 Macro has too many parameters de Deceit
33. L TIN oe A OS 71 STUPE nr EE EO OR EE ml ie EE de 71 ME OS EE OO Dok BAND U 72 EE PE da dd NE eel SE ah a ne 72 EE EE EE EE EE OE ys 72 EE ER EE EE RA ME RE OE N 73 TA OE Ed RE ER ET N Er 73 UL ZC EE REED E EE De ee A EN Ge e Pe De Ee Gee LEE 73 5 ADVANCED PROGRAMMING TECHNIQUES esse se ssssssse sesse se sees se se see se see 74 5 1 WRITING SIMPLE ASSEMBLY LANGUAGE SUB ROUTINES eise ee esse ees ee ee ee ee ee ee ee 74 5 2 ASSEMBLY LANGUAGE FUNCTION S RETURN VALUE 2 sesse esse se se ees se se ee ee ee se ee ee ee ee 75 5 3 ASSEMBLY LANGUAGE FUNCTIONS WITH PARAMETERS iese ss ees se ee ee ee ee se ee ee ee ee 76 5 3 1 Accessing parameters in assembler program ees se ee se ee Re ee RR ee 76 5 4 CALLING C FUNCTIONS FROM ASSEMBLY LANGUAGE esse esse se sees ee se ee ee ee ee ee ee ee ee ee 77 add Passing parameters EA TA Dis Oe De ee GE AA ena 77 APPENDIX A ERROR AND WARNING MESSAGE G cssssscssssssssccsssssccsssses 79 HOW CAN I SEE ALL OF THE ERROR WARNING MESSAGES iese esse ese ee ee se ee ee ee se ee ee ee 79 MAR NING MESSAGES ER ee ee rn OG Ge de EE ee ea er ae ss 79 SC51 User s manual 6 http www spjsystems com Parameter paraname never used Si Caste ee DE ee ii dali 60 Local variable localname declared but never used ie sesse esse ees se ee ee ee ee 80 No declaration for function funcname a aed 60 ERROR MESSAGES sek ed se tiaras ee loci 80 Declaration STE HOE MEES A De EG Ge ee
34. Prototype in macros31 h Remarks This function writes the appropriate byte in TMOD If gate is 1 then the GATE bit in TMOD for Timer 1 will be set otherwise it will be cleared If c t is 1 then Timer 1 will be used as a counter otherwise it will be used as a timer mode can be either 0 1 or 2 Return value None See also set tO mode Function Sets timer 0 or 1 count Syntax void set tcnt int tnum unsigned int count Prototype in standard h Remarks This function sets the count high and low for timer 0 or 1 tnum can be O or 1 count is the count which will be loaded in either thO and tlO or thl and tll Return value None Function Returns the sine of the argument Syntax include lt math h gt float sin float x Prototype in math h Remarks This function is NOT included in the library but it is given in the form of source code It s source code can be found in SOURCE CFILES MATH C Return value sin returns the sine of x See also cos asin SC51 User s manual 66 http www spjsystems com Function Returns the hyperbolic sine of the argument Syntax include lt math h gt float sinh float x Prototype in math h Remarks This function is NOT included in the library but it is given in the form of source code It s source code can be found in SOURCE CFILES MATH C Return value sinh returns the hyperbolic sine of x See also sin Function Sends formatted output to t
35. RES De AS 84 Invalid Statem en oe E ee E Ge ee ee 84 Line FOG OUES EE ee es oe Re eg eg Ee oo TA enke eye ae Re EE Rosas 84 LOGIN RE EE RR N N 84 Too many gt 128 SFR declarations Ad 65 bit type local var para array not allowed A Ge A 85 pointer to bit variable snot allowed iste se EE Ee Ns ee Ke Ee ese ee Ee ek N ee sg ek 65 SC51 User s manual 7 http www spjsystems com SC51 User s manual http www spjsystems com 1 Introduction Thank you for purchasing SC51 Now you can write 8051 applications in C and debug simulate those without the target hardware How to use this manual This manual is intended to be read from start to end so you learn about all the features of this compiler However the library functions description may be skipped initially and it can be referred to when you actually start writing applications The chapter 2 provides instructions to install the software Chapter 3 gives you a general idea of the features of the software After reading chapter 3 you may start actually using this software Chapter 4 contains detail information about Configuration Chapter 5 contains information about Run menu options For any questions or comments about the product please feel free to contact us at SPJ SYSTEMS 101 Beaver Grandeur Baner Road Pune Pin 411 045 Tel 91 20 7293002 Fax 91 20 7293003 E mail spj spjsystems com Web site http www spjsystems com SC51 User s manual
36. SCS1 C Compiler for 8051 User s Manual SPJ Systems 101 Beaver Grandeur Baner Road Pune 411045 Tel 91 20 7293002 Fax 91 20 7293003 http www spjsystems com Terms and Conditions for use of the software For the purposes of this document the term THE PRODUCT shall be used to refer to SC51 C compiler for 8051 Terms and Conditions 1 2 3 4 5 You may make a backup copy of THE PRODUCT and you may install THE PRODUCT on your computer systems hard disk but only one copy of THE PRODUCT may be in use at any one time If you make any modifications to THE PRODUCT the modified code shall regardless of the extent of modification remain the property of SPJ Systems You may not remove or alter any copyright notices contained in the source files documentation executables or any part of THE PRODUCT You may not re distribute any part of THE PRODUCT or any materials which are based on or otherwise derived from any portion of THE PRODUCT Any and all copies of THE PRODUCT must be retained in your possession at all times You are granted permission to distribute any programs that you develop with THE PRODUCT provided that they are not based on or otherwise derived from any source code contained in THE PRODUCT You agree to use THE PRODUCT entirely at your own risk and assume all responsibility for such use The author and distributors of THE PRODUCT do not warrant it fit or suitable for any particu
37. al 49 http www spjsystems com bit isspace char c s Prototype in ctype h Remarks isspace is a function that classifies ASCII coded character values It returns 1 for true and 0 for false Return value isspace returns 1 if c is a space tab carriage return or newline Function Character classification function Syntax include lt ctype h gt bit isupper char c i Prototype in ctype h Remarks isupper is a function that classifies ASCII coded character values It returns 1 for true and 0 for false Return value isupper returns 1 if c is an uppercase letter A Z Function Character classification function Syntax include lt ctype h gt bit isxdigit char Cc 5 Prototype in ctype h Remarks isxdigit is a function that classifies ASCII coded character values It returns 1 for true and 0 for false Return value isxdigit returns 1 if c is a hexadecimal digit 0 9 A P a f Function Converts an integer into ASCII string Syntax include lt stdlib h gt void itoa c31 int val char dest int ndigits Prototype in stdlib h Remarks itoa c31 converts an integer number val into ASCII string dest containing exactly ndigits digits SC51 User s manual 50 http www spjsystems com Return value None See also ltoa_c31 Function Gives long absolute value Syntax include lt stdlib h gt long int labs long int x Prototype in stdlib h Remarks lab
38. alue into ASCII string such as sprintf or Itoa_c31 and insert a decimal point at 3 positions from the right long int arithmetic produces much smaller and faster code as compared to float arithmetic Use the float data type only when you really need to store and process floating point numbers ane Xen Kaun SC51 User s manual 88 http www spjsystems com
39. be printed Undefined label If a label corresponding to a goto statement is not defined till the end of the function this error message will be printed Undefined macro If you try to undefine a macro using undefine which is not defined at all this error message will be printed Macro Parameters missing If you have defined a macro with parameters you must pass the same number of parameters while using the macro If in the macro call the parameters are missing this error message will be printed Too many few parameters passed to macro If you have defined a macro with parameters you must pass the same number of parameters while using the macro If in the macro call the no of parameters passed is not same as the no of parameters required this error message will be printed Macro definition syntax error If a syntax error is detected in a macro definition this error message will be printed e g if you attempt to use a keyword as the macro name this error message will be printed SC51 User s manual 83 http www spjsystems com Unexpected else or endif The else or endif must have a corresponding ifdef or ifndef If else or endif are found out of place this error message will be printed Too many macro definitions As you keep defining macros the compiler remembers all the macro definitions But when the compiler runs out of memory to store any more macro definitions this error message
40. ble values 0 or 1 e In expression you can combine variables of different data types e g you can add an integer variable to a floating point variable However the same is not applicable to bit data type i e if one of the operands is a bit type variable then the other operand also must be another bit type variable not even a constant of some other type e Only a certain operations can be performed on bit type variables See the details below in section 3 7 Operators e You can not declare a pointer to bit However pointers up to one level to other data types can be declared 3 5 Type Conversions In an expression if the two operands of a binary operator are of different types then the compiler will attempt to convert one of the operands into the type of the other The compiler uses some rules to do this as follows If either of the operands is of type bit then compiler prints an error type mis match since it can not convert bit type to any other type or vice versa Otherwise if either of the operands is of type float then the other operand is converted to float type Otherwise if either of the operands is of type long int or unsigned long int then the other operand is converted to the same type Otherwise if either of the operands is of type int or unsigned int then the other operand is converted to the same type SC51 User s manual 14 http www spjsystems com Thus
41. blishers are available to learn more about C language This chapter describes syntax related information applicable to this implementation of C Compiler and not necessarily of the C language in general 3 1 Comments The character string marks the beginning of a comment and the string marks the end of it e g printf Some message n This is a comment Comments may be spread over multiple lines sy However nested comments are not allowed e g comment line 1 fe RED VY last line sy This will produce an error because the string after line 2 marks the end of comment and hence the string appearing again after last line will generate an error SC51 User s manual 11 http www spjsystems com C style of comments is also supported i e all stuff followed by up to the end of the line is treated as comment e g printf Some message n This is C style comment 3 2 Identifier An identifier is just the name you give to a variable function or other user defined objects An identifier can contain letters A Z a z and digits 0 9 as well as the underscore character _ However an identifier can only start with a letter or an underscore Case is significant i e varl is not the same as Varl The maximum length of an identifier is 20 characters 3 3 Keywords Following is a list of keywords reserved by the compiler These can not be used as
42. calls the put char function to output each character Thus if put char function is re written by the user to send the output to some other device the output of puts will also go to the new device Return value Returns the last character written See also putchar Function Performs formatted input Syntax include lt stdio h gt int scanf char format Related functions SC51 User s manual 58 http www spjsystems com int sscanf char src char format Prototype in stdio h Remarks The scanf family of functions scan input fields one character at a time and convert them according to a given format They accept a format string i e the format parameter that determines how the input fields are to be interpreted They apply the format string to a variable number of input fields in order to format the input Then they store the formatted input in the addresses given in arguments after the format When it encounters it s first format specification in the format string it scans and converts the first input field according to that specification then stores the result in the location given by the first address argument it then scans converts and stores the second input field then the third etc The scanf function gets input from the standard input device i e normally the on chip serial port It actually calls the getchar function to read each character from the standard input device If you write your own getchar
43. ch means it can point to any memory area Generic pointers are 3 byte pointers Here are some examples of pointer variable declarations char p_ch generic pointer 3 byte length idata char p_ch2 pointer to idata memory area 1 byte length xdata int p_xi pointer to xdata memory area 2 byte length Local variables and parameters are always pushed on stack which means they are always stored in internal data memory regardless of memory model Hence memory area specifier can not be used on local variables or parameters unless it is a pointer variable In case of pointer variables the memory area specifier does not affect the location of pointer variable itself but it restricts the pointer to point only to the specified memory area Hence use of memory area specifier on pointer variables is always allowed even if the pointer variable is local global or a parameter All library functions of SC51 which take pointer parameter s use generic pointers User defined functions may use memory specific or generic pointers Declaring variables at specific address in Internal External RAM This compiler allows the programmer to declare a variable at a specific address The syntax for doing so is as follows var_type addr var_name or var_type laddr var name where var_type is any legal data type except bit and var_name is any legal identifier name and add
44. d Prototype in standard h Remarks It initializes the serial port for a certain mode If you are going to use printf function you must first initialize the serial port Calling this init_ser function is just one method of initializing the serial port This function puts the Timer in 8 bit auto reload mode and it puts the serial port in mode 1 with receiver enabled It sets the baudrate at 2400 assuming 12 Mhz crystal The source code of this function is available to the users Return value None See also printf Function Reads a byte from a hardware port Syntax unsigned char inportb int portid Prototype in standard h Remarks inportb reads a byte from a location in data memory whose address is specified by portid Return value inportb returns the value read SC51 User s manual 47 http www spjsystems com See also peekb outportb Function Converts an integer number into a BCD string Syntax void int2bcd int value char dest int ndigits Prototype in standard h Remarks Converts value into an unpacked BCD string which is ndigits digits long and places the string in dest Return value None See also bcd2int Function Character classification function Syntax include lt ctype h gt bit isalnum char c Prototype in ctype h Remarks isalnum is a function that classifies ASCII coded character values It returns 1 for true and O for false Return value isalnum ret
45. d bit type local var para array not allowed A bit type variable must be declared as a global variable only If you attempt to declare a bit variable as a local variable or as a parameter this error message will be printed Also arrays of bit variables are not supported in this version of the compiler If you attempt to declare an array of bit type variable this error message will be printed pointer to bit variable not allowed The current version of the compiler does not support pointer to bit type variable If you attempt to declare a pointer to a bit type variable this error message will be printed SC51 User s manual 85 http www spjsystems com Appendix B Limitations of the compiler There are certain areas of the compiler that have known limitations or bugs SPJ Systems will attempt repair these problems in future versions of the C Compiler Until that version is released you should be aware of these limitations This appendix describes all such known limitations and known bugs which are reported and not corrected yet You will also find some useful suggestions in order to use the compiler in a better and more efficient way in Appendix C LIMITATIONS AND BUGS 1 Only global variables can be initialized during declaration In case you attempt to initialize a local variable the compiler will produce some Assembler error during the Assembler Pass 2 If you want to initialize a character array to a very long
46. data Internal data memory directly accessible 00H 7FH access using direct and indirect addressing mode idata Internal data memory indirectly accessible OOH FFH access only using indirect addressing mode bdata Internal data memory bit addressable 20H 2FH access using direct and indirect addressing mode as well as bit addressing capability xdata External data memory access using indirect OOOOH FFFFH addressing using movx dptr instruction pdata Paged External data memory access to only PPOOH PPFFH one 256 byte page of external data memory where PP is using movx r0 or movx Orl instruction page address output on P2 code Internal or External program memory 0000H FFFFH read only access using move instruction In your target hardware the actual amount of memory available may be less than the ranges mentioned above In some cases some memory areas maybe entirely missing for example some designs do not use external data memory at all which means xdata and pdata is missing The compiler and linker generally assign appropriate address to all variables unless the address is specified by user with notation By default all global variables are assigned addresses in data memory area 1f small memory model is used or in xdata memory area if large memory model is used It is possible to override this default and force the compiler to keep variables in other memory areas regardle
47. e case or default keyword inside a switch statement must be followed by a colon If this is missing the compiler prints this error message Too Many Default Statements OR default May be Outside of switch The default keyword must be used inside a switch statement However when the compiler encounters a default statement which is NOT inside a switch statement it will print this error message Also you may use the default keyword only once in a single switch statement If you tried to use more than one default in a single switch statement then also the same error message is printed SC51 User s manual 82 http www spjsystems com Type Mismatch If the types of two operands are not matching with each other this error message will be printed However this does not mean that both the operands must be of the SAME type Even the types are not same the compiler generates code to convert one of the operand into that of the other However this may not be always possible e g a bit type variable can not be converted to any other type Hence for example if you try to add bit type variable into an int type variable it will produce this error Too many goto statements max 10 In a single function you may not write more than 10 goto statements If you attempt to use goto more than 10 times in a function this error message will
48. e lt macros31 h gt disable Prototype in macros31 h Remarks Clears only bit 7 of IE so that all interrupts remain disabled Return value None See also disable_all enable Function Disables interrupts Syntax include lt macros31 h gt disable _all Prototype in macros31 h Remarks Clears all bits of IE so that all interrupts remain disabled Please note the subtle difference between disable and disable all Return value None SC51 User s manual 36 http www spjsystems com See also disable enable all Function Disables INTO external interrupt Syntax include lt macros31 h gt disable _ex0 Prototype in macros31 h Remarks Clears bit 0 of IE so that external interrupt INTO remains disabled Return value None See also enable ex0 Function Disables INT1 external interrupt Syntax include lt macros31 h gt disable _exl Prototype in macros31 h Remarks Clears bit 2 of IE so that external interrupt INT1 remains disabled Return value None See also enable exl Function Disables receiver of serial port Syntax include lt macros31 h gt disable rx Prototype in macros31 h Remarks Clears bit 4 of SCON so that serial port s receiver remains disabled Return value None See also enable_rx SC51 User s manual 37 http www spjsystems com Function Disables serial port interrupt Syntax include lt macros31 h gt disable_ser Prototype in macros
49. e nn iii 26 4 SC51 LIBRARY FUNCTIONS REFERENCE eee esse ee esse sees se sees se ee es ese se ee se ge ee eg 27 LIST OF FUNCTIONS IN ALPHABETICAL ORDER sesse ees se ee ee ees se ee ee ee ee ee se ee ee ee ee ee ee ee ee 27 ADS re Cased ee AREA ASE T E AAA 31 ACOS AS ar a HT 31 A a EE 31 WAL OF RR EE EE ORE EE EED RE ET OE O 32 EA LE EES BEE SE SEEN ELE 32 A EE inns SEERE TE EE EA aaa eae 32 DCU PAA AT ER A EE EE N Ee N 33 AE EE TA RE OE OE ea a OE Pad sl EE 33 Gl double DEU see NE ee ER ee ee atl gota ee a EE EG 33 CUTE site IE N atic aa erates VE IA ED eN 33 LI DU SE esi nce OE E 34 SC51 User s manual 3 http www spjsystems com GOS EE A ee EE RE OA OEE E EEE E A EE ede 34 CDNA EE colic tannin Pisin ce OE RE OE AE AE AE ae 35 EE EE RE EE NE N EE N AE RE ED N EE n 35 LISD Ce ME ES N OE EN OR N EEN 36 disablesalls ee o ee Pe eg 36 disable EXO ERGE EE AA AA A A E O 37 OYAN AE A A RERA AE A o EE E A DE en EL LE 37 disablet ES AA a RD Pa Pete IE 37 disable SOR es ESE AAA Ee ee E Ee REIN AA N ed AA AS 38 ASADO N ER RE RE REECE CETTE PEPER RE 38 disable HEESE EE A dt CEE TET EECR TTC CITE 38 ISDE 12 RE EE EE EA OE DN AE MESSE SEERE ERE 39 Enable SELDE GE RE EE GE ER Ad ES 39 enable Alli ii OE OE tendere se 39 RR OE EE iso 40 ER EE EE EE N EE N EE N RE 40 CNADLE TE EE LE EE OE Sb 40 CNA DIOS 2 PEE T OE EE GE a E DE GE SN Te 4 enable ONE EE N t a 4 enable tee ed GE O ES Ee ee EG SESE 4 RA NE OE Rd RE EO TC ETE 42 AE ME
50. er header files which define the SFRs for the corresponding CPUs We have supplied number of header files which contain SFR declarations for many different 8051 derivatives These header files are in the folder INC There is 1 folder for each manufacturer which contains the header SC51 User s manual 18 http www spjsystems com files for all 8051 derivatives manufactured by that particular manufacturer You may include the appropriate header file in your C program If you are using any other 8051 derivative for which no header file is supplied you can create your own header file and include it in your C program Thus you can use declared SFRs as global variables of unsigned char type You can use these in any expressions except that you can not use the amp address of operator with these variables because these are not really variables but are pseudo variables and these are not indirectly accessible 3 10 2 Assembly language interface Parts of a program may be very time critical e g you may like an interrupt service routine to finish in as small time as is possible For this reason you may like to write part of the program in assembly language This is made possible by providing assembly language patch up facility You may write part of the program in assembly language ina SEPARATE FILE When you invoke the compiler use the a option to specify the ASM file name i e include Aasm_file_name in the command line before the
51. eturn value type could be bit To access a bit of a bit accessible SFR you can make use of BIT declarations e g to set bit 3 of P1 you can write either P1 8 or BIT pl 3 ples pe Define a BIT sy Bl 8 D 3 set the bit The later method is much more efficient If you need a software delay it is more convenient efficient and accurate to use the library function delay or delay_ms instead of writing empty for loop etc Please refer to the chapter Library functions reference for details about the delay and delay_ms functions 10 Floating point numbers are fairly complex data types and the compiler needs to generate number of sub routine calls for even basic arithmetic operations on floating point numbers Hence the code generated for floating point arithmetic is generally longer and runs slower Whenever possible avoid the use of float numbers In many situations long int data type can be used instead of float data type to represent even fractional numbers if they are fixed point For example if it is required to store only 3 digits after the decimal point and maximum 5 digits before the decimal point for a certain variable then it may be possible to use the long int data type instead of float You only need to remember that the value of the variable TheRealValue 1000 Thus to display the value you may use a suitable function to convert the long int v
52. ght like to assign a symbolic name to P1 0 Exactly this can be done using the BIT keyword The syntax for using it is BIT identifier name value Please note that a BIT statement is NOT followed by a semicolon The identifier can be any legal identifier name which is not previously declared The value must take this forms sfr name bit addr where sfr name can be the name of any bit accessible SFR of 8031 and bit addr may be any value between 0 and 7 Here are some examples of correct and incorrect BIT statements BIT motor pl 0 correct BIT limit switch p3 6 correct BIT motor p3 wrong because the bit_addr is missing BIT something dpl 2 wring because dpl is not a bit accessible SFR Once you have defined a symbol using the BIT keyword then onwards you can use it in your program as if it were a variable of bit type e g if you have defined motor and limit switch as above you may write if limit switch motor 0 else motor 1 The above two statements are equivalent to checking bit 6 of P3 and accordingly either setting or clearing bit 0 of P1 SC51 User s manual 20 http www spjsystems com 3 10 5 Memory area specifiers data idata bdata xdata pdata code The 8051 architecture uses number of logically separate memory areas The different memory areas have been assigned names as below Memory Memory area description Address range Area name
53. he destination string Syntax int sprintf char dest char format Prototype in stdio h Remarks The sprintf function sends formatted output to the destination string dest parameter The second parameter format specifies how the output is to be formatted The first and second parameters are mandatory The sprintf function beheaves almost the same as printf function except the difference in output location The output of print f goes to standard output device which is generally the on chip serial port but the output of sprint f goes into a character string pointed by the first parameter dest For details about the format parameter please see the description of printf Return value The sprintf function returns the number of bytes copied to the destination string See also printf Also please look at the file PRINT C in EXAMPLES PRINT directory Function Returns the square root of the argument Syntax include lt math h gt float sqrt float x Prototype in math h SC51 User s manual 67 http www spjsystems com Remarks This function is NOT included in the library but it is given in the form of source code It s source code can be found in SOURCE CFILES MATH C Return value sqrt returns the square root of x Function Reads formatted input Syntax include lt stdio h gt int sscanf char dest char format Prototype in stdio h Remarks See scanf Function Starts timer 0
54. iable was defined No declaration for function funcname If a function is called in an expression and if it is not earlier defined or declared this warning message will be printed Error Messages Almost all of the error messages also display the source file name and the line number which caused this error message The meaning of all error messages are described below Declaration Syntax Error This error message is generally caused by an incorrect variable or function declaration or definition Check the spellings and syntax of the given line number Also see the list of supported data types Redeclaration of identifier OR function If a variable or function is defined more than once then it causes this error message However 2 or more variables of the same name can exist provided one of those is a global variable and the other one is a local variable or a parameter Too Many Identifiers If the compiler runs out of memory for the symbol table it produces this error message Check for any unused variables functions and remove them if possible Unknown Identifier If you attempt to use a variable without declaring it this error message will occur Please check the spellings SC51 User s manual 80 http www spjsystems com Invalid Identifier If an identifier is badly defined this error will occur Please see the rules of defining an identifier in Language Reference in this manual Too many erro
55. itoa_c31 SC51 User s manual 52 http www spjsystems com memset Function Sets n bytes a block of memory to byte c Syntax include lt mem h gt void memset void s int c int n Prototype in mem h string h Remarks memset sets the first n bytes of the array s to the character c Return value memset returns s Function Splits into mantissa and exponent Syntax float modf float x float ipart Prototype in math h Remarks See fmod Function Copies a block of length bytes Syntax include lt mem h gt void movmem void src void dest unsigned length Prototype in mem h Remarks movmem copies a block of length bytes from src to dest Return value None Function Outputs a byte to a hardware port Syntax void outportb int portid unsigned int value Prototype in standard h Remarks outportb is a function that writes the byte given by value to the location in data memory whose address is specified by portid Return value None See also inportb pokeb SC51 User s manual 53 http www spjsystems com Function Returns a byte of memory Syntax char peekb unsigned addr Prototype in standard h Remarks peekb returns the byte at the location in program memory whose address is specified by addr Please note the difference between inportb and peekb functions inportb reads from data memory whereas peekb reads from program memory Return value peekb returns the val
56. l padding dest The target string dest might not be null terminated if the length of src is maxlen or more Return value strncpy returns dest Function Converts lower case letters in a string to uppercase Syntax char strupr char s Prototype in string h Remarks strupr converts lower case letters a z in string s to uppercase A Z No other characters are changed Return value strupr returns s See also strlwr SC51 User s manual 71 http www spjsystems com Function Trigonometric tangent function Syntax include lt math h gt float tan float x Prototype in math h Remarks This function is NOT included in the library but it is given in the form of source code It s source code can be found in SOURCE CFILES MATH C Return value tan returns the tan of x See also cos sin tanh Function Hyperbolic tangent function Syntax include lt math h gt float tanh float x Prototype in math h Remarks This function is NOT included in the library but it is given in the form of source code It s source code can be found in SOURCE CFILES MATH C Return value tanh returns the hyperbolic tan of x See also cos sin tan Function Translates characters to lower case Syntax char tolower char ch Prototype in ctype h Remarks tolower is a function that converts a character ch in the range 0 to 255 to its lower case a z value if it was uppercase A Z a
57. land 0 lt f lt y SC51 User s manual 44 http www spjsystems com modf breaks x into two parts the integer and the fraction It stores the integer in ipart and returns the fraction Return value fmod returns the remainder f where x iy f as described modf returns the fractional part of x Function Splits a float number into mantissa and exponent Syntax float frexp float number int power Prototype in math h Remarks See exp Function Reads a byte from the serial port Syntax include lt standard h gt int getbyte Prototype in standard h Remarks Waits for some time or until a byte is available from the on chip serial port of the 8031 Return value Ifa byte was available returns the received byte Otherwise returns 1 See also ser_rdy sendbyte Function Reads a byte from the 8279 based keyboard Syntax include lt hardware h gt int getch Prototype in hardware h Remarks Waits till a byte is available from the keyboard which is connected to 8279 When a key is pressed reads it s scancode from 8279 If you want to use this function you must declare the address of 8279 using the peripheral keyword e g peripheral 8279 0x4000 SC51 User s manual 45 http www spjsystems com Return value Returns the scancode read from 8279 See also kbhit Function Reads a character from standard input device Syntax include lt stdio h gt char getchar
58. lar purpose SC51 User s manual 2 http www spjsystems com CONTENTS 1 INTRODUCTION osse es sine is Geo ke Re eed de Ge is ees Ge NE be eed ee Ge ok Ad ios 9 2 INSTALLATION ER N EE EE EE N EE N EG 10 3 LANGUAGE REFERENCE sees ien ees oos sesse Se ese ke pd eon ede de ske oe Gee ie deer egg seep Sie 11 3 1 COMMENTS RE tees bespieden ine dida 11 32 SADDENS I So GO os essen as eae ets oe a os eae NS aed a as oa SER 12 Died KEYWORDS de NA E AT AA A A anita ade 12 SR VUUR ds EO EE ER EE dde 13 3 3 7 TYPE CONVERSIONS ud o DR oe 14 3 0 7 CONSTANTS A een elem eles tse 15 3 Te OPERATORS Se Goal ee ac ERE LEN ed ED eS Ne hile Sa a ea 15 3 9 FUNCTION PROTOTYPES dictada dto adios 16 3 9 COMPILER CONTROL LINES vna dai ia deka eN Su Eps Ge SN EG 17 3 10 ADDITIONAL FEATURES SG EES se ees ie ee codes be eene See ee Die 18 3 10 1 Using Special Function Registers SFR Ms esse Ses se De Ge Ne es See N ee 18 3 10 2 Assembly language interface Li EE ER ee N Ee ee eg AG Re enlace 19 LOS ITheasm N AMORE ET DEER OE EER 19 3 LOA TEBII KEYWOTA A A AA DE E ale aE ate 20 3 10 5 Memory area specifiers data idata bdata xdata pdata code 21 3 10 6 Memory specific and generic pointers iese ese ee ER Re ee ee ee RA ee 22 3 10 7 Declaring variables at specific address in Internal External RAM 23 3 10 8 interrupt functions and the using directive Messen ee ee ee Re ee 24 3 10 9 Absolute Register Address M8 ss ess
59. ll others are left unchanged Return value tolower returns the converted value of ch if it is uppercase all others it returns unchanged SC51 User s manual 72 http www spjsystems com toupper Function Translates characters to uppercase Syntax char toupper char ch Prototype in ctype h Remarks toupper is a function that converts a character ch in the range 0 to 255 to its uppercase value A Z if it was lower case a z all others are left unchanged Return value toupper returns the converted value of ch if it is lower case it returns all others unchanged Function Converts an unsigned integer into ASCII string Syntax include lt stdlib h gt void ui2a_c31 unsigned int val char dest int ndigits Prototype in stdlib h Remarks ui2a c31 converts an unsigned integer number val into ASCII string dest containing exactly ndigits digits Return value None See also itoa_c31 Function Converts an unsigned integer number into a BCD string Syntax finclude lt stdlib h gt void ui2bcd unsigned int value char dest int ndigits Prototype in stdlib h Remarks Converts value into an unpacked BCD string which is ndigits digits long and places the string in dest Return value None See also int2bcd SC51 User s manual 73 http www spjsystems com 5 Advanced Programming Techniques 5 1 Writing Simple Assembly Language Sub routines I
60. mbler instructions that often use registers RO R7 These can be accessed as registers with the names RO R7 or as direct addresses in data memory In the later case the compiler uses pre defined register address symbols ARO AR7 Depending on the currently selected register bank the ARn symbol translates to appropriate address For example if banko is selected then AR4 translates into 04H If bank1 is selected AR2 translates into OAH In this case the function will work correctly only if the same register bank is selected at runtime This maybe a problem in case of some functions For example consider a function f1 which is called by main as well as an Interrupt function By default register bank0 is selected for all non interrupt functions But Interrupt functions must select another register bank with the using keyword Thus when function f1 is called sometimes register bankO will be selected but at some other times another register bank maybe selected Obviously if absolute register addressing is used during function fl it will result in malfunctioning The SC51 provides a way to disable or enable absolute register addressing The controls NOAREGS and AREGS can be used in conjunction with pragma The syntax is as follows pragma NOAREGS this point onwards absolute register addressing will be disabled write functions like fl here so that absolute register addressing will not be used pragma
61. ng with subsequent characters until the corresponding characters differ or until the end of the strings is reached Return value strcmp returns a value that is lt O if sl is less than s2 O if sl is the same as s2 gt 0 if sl is greater than s2 Function Copies one string into another Syntax char strcpy char dest char src Prototype in string h Remarks copies string src to dest stopping after the terminating null character has been moved Return value strcpy returns dest Function Calculates the length of a string Syntax finclude lt string h gt int strlen char s Prototype in string h Remarks strlen calculates the length of s Return value strlen returns the number of characters in s not counting the null terminating character SC51 User s manual 70 http www spjsystems com striwr Function Converts uppercase letters in a string to lower case Syntax char strlwr char s Prototype in string h Remarks strlwr converts uppercase letters A Z in string s to lower case a z No other characters are changed Return value strlwr returns a pointer to the string s See also strupr Function Copies a given number of bytes from one string into another truncating or padding as necessary Syntax finclude lt string h gt char strncpy char dest char src int maxlen Prototype in string h Remarks strncpy copies up to maxlen characters from src into dest truncating or nul
62. r i or u When input size modifier is not used these type characters need a 2 byte argument and it is interpreted as signed or unsigned integer If input size modifier 1 is specified as in S1d or S1u then a 4 byte argument long int orunsigned long int is needed On the other hand if input size modifier b is used as in Sbd or Sbu then single byte char or unsigned char argument is needed In this implementation of the compiler the on chip serial port of 8051 is considered as the standard output device However the user can change this with little effort The printf function actually calls the function put char to output each character The source code of the put char function is available to the users If you want the standard output device to be something else say LCD you simply need to rewrite the put char function If you have written a function named as put char somewhere in your C program then the compiler will not link the default put char function from the library Then if you call printf function it eventually calls put char to send the output In this case your putchar function will be called rather than the default put char function which is there in the library Return value The printf functions return the number of bytes sent to the standard output device to destination string See also sprintf putchar Also please look at the file PRINT C in EXAMPLES PRINT folder Function Sends a byte
63. r is any hexadecimal constant In the first case the variable var_name is assigned an address addr in external RAM and in the later case the variable var_name is assigned an address addr in internal RAM Thus in a variable declaration if the variable type is followed by followed by a hexadecimal constant address then the variable will reside at the specified address in external RAM On the other hand if the variable type is followed by I there should not be any space between and I followed by a hexadecimal constant address then the variable will reside at the specified address in internal RAM This is further illustrated in following example unsigned char 0x6000 dat_8279 i e amp dat_8279 is 0x6000 in external RAM unsigned char 0x6001 cmd_8279 i e amp cmd 8279 is 0x6001 in external RAM int I10x2d varl SC51 User s manual 23 http www spjsystems com 3 10 8 i e amp varl is 0x2d in Internal RAM unsigned char ch this is ordinary variable It s address will be decided by the compiler Also whether it will reside in internal RAM or external RAM will depend on the memory model used void main f cmd 8279 ch an alternative without using would be outportb 0x6001 ch varl dat 8279 an alternative without using would be varl inportb 0x6000 Thus declaring variables at a specific address results
64. r is mandatory After that there may be a variable number of parameters Format specifications have the following form width prec l b type where flags is an optional sequence of flag characters width is an optional width specifier prec is an optional precision specifier 1 b is an optional input size modifier type is the conversion type character Here is a list of conversion type characters the type of input argument accepted by each and in what format the output will appear assuming no flag characters width specifiers precision specifiers or input size modifiers were included in the format specification The effect of optional characters and modifiers is described later SC51 User s manual 55 http www spjsystems com Type Input Argument Format of output Character integer int signed decimal integer unsigned int or long int unsigned long int integer int signed decimal integer unsigned int or long int unsigned long int integer int unsigned decimal integer unsigned int or long int unsigned long int floating point float signed value in the form dddd ddd character char string pointer outputs characters until a null terminator is found the character is printed The optional flag character can be used to get left justified output If this is not specified the output is right justified How the width specifier affects the output Width How output
65. rations should be of the form extern memory_area_specifier const data_type var_name value where extern is optional keyword indicating that variable is defined in another module memory_area_specifier is optional one of the valid memory area specifiers data_type must be a valid data type var_name must be a valid identifier name Optionally the variable maybe initialized 5 Use of memory area specifier is allowed only on global variables and pointer variables Please see next section for more about memory area specifiers on pointers 3 10 6 Memory specific and generic pointers Use of memory area specifier on a pointer variable has different effect than non pointer variables As explained above use of memory area specifier on non pointer variables forces the variable to reside in the specified memory area However pointers always reside in the default memory area even if memory area specifier is used If a pointer is declared with memory area specifier it becomes a memory specific pointer which means it can point only to the specified memory area Such memory specific pointers are 1 byte or 2 byte pointers If a pointer is pointing to data idata bdata or pdata area it is 1 byte pointer If a pointer is pointing to xdata or code area it is 2 byte pointer If a pointer is declared without SC51 User s manual 22 http www spjsystems com 3 10 7 any memory area specifier it becomes a generic pointer whi
66. rs If the compiler encounters too many error messages while compiling your program it will print this message and stop the compile process Please note that this indicates that your program has not been completely compiled i e there may be more errors which are not detected yet Please correct the displayed errors and compile again Invalid Statement Syntax error If the general syntax rules of C language are not followed one of the above two general error messages is printed e g the if keyword must be followed by a valid expression enclosed in a pair of parenthesis If this is missing you may see this error message This 1s just one example there may be numerous situations under which you will see this message Mismatch brackets If in an expression the parenthesis and or the square brackets and are not in matching pairs this error will be printed If in your program the curly brackets are not in matching pairs then also you will see the same error message Too Many Brackets An expression may contain any number of parenthesis or square brackets provided they are in matching pairs However the more brackets in an expression the more memory is required by the compiler Thus when the compiler runs out of memory while sorting out an expression this error message is printed Statement Missing In C language each statement must be followed by a semicolon barring
67. s x y 7S Now 7S will be considered as a single byte unsigned char value 07H Since the two operands y and 07H have same data types no code is generated for conversion to int Instead the compiler will simply generate the mul ab instruction to perform the 8 bit X 8 bit multiplication thus the generated code will be much smaller and it will run much faster Generally use as small data type as is sufficient Using int or unsigned int is better than using long int or unsigned long int Using char or unsigned char 1s even better Instead of using inportb and outportb functions it is much efficient to use a variable declared at a specific address in external RAM e g instead of writing outportb 0x6000 0 SC51 User s manual 87 http www spjsystems com 6 7 8 9 it is better to write dat 8279 0 where dat 8279 is a variable defined as follows unsigned char 0x6000 dat 8279 Wherever possible use unsigned data types instead of signed i e unsigned char instead of char unsigned int instead of int andunsigned long int instead of long int Since the 8051 does not have any instructions to perform signed arithmetic it is easier to perform arithmetic operations on unsigned number Whenever a variable is going to hold only two possible values 0 or 1 or TRUE or FALSE it is efficient to use bit variable instead of int or char Even a function s r
68. s Always define global variable in your C program so that the reguired space gets allotted to them Use only the names of these variables as internal external data memory addresses e g if you want to use a byte location in external data memory you should declare a unsigned char type global variable in your C program as xdata unsigned char asm var In your assembly language function you can use it as mov dptr _asm_var load the addr in DPTR movx a dptr read the value do some processing movx dptr a write back the value If you stick to these rules chances of system crash will be far too less 5 2 Assembly Language Function s return value Suppose you want the assembly language function to return some value follow these guidelines In your C program you must put the function s declaration e g unsigned char some func E Then you may call this function as and when required e g value some_func 25 In assembly language you write _some_func some code here finally compute the return value in Acc and then store mov myacc a the return value put in proper place ret SC51 User s manual 75 http www spjsystems com Note that the retum value should be always put in the internal RAM location myacc Depending on the type of return value you may write 1 to 4 bytes from location onwards e g in case of int type return value you should write the LSByte of the return value at
69. s computes the absolute value of the parameter x Return value On success labs returns the absolute value of x There is no error return See also abs Function Calculates value 22YT Syntax float ldexp float value int power Prototype in math h Remarks See exp Function Calculates natural logarithm of value Syntax float log float value Prototype in math h Remarks See exp Function Calculates base 10 logarithm of value SC51 User s manual 51 http www spjsystems com Syntax float log10 float value Prototype in math h Remarks See exp Function Converts a long int number into BCD string Syntax include lt stdlib h gt void long2bcd long int value char dest int ndigits Prototype in stdlib h Remarks long2bcd converts value into an unpacked BCD string having ndigits digits It puts the BCD string in dest Return value None See also int2bcd Function Separates the low order nibble Syntax unsigned char lo_nibb unsigned char ch Prototype in standard h Return value Returns the low order nibble of ch See also hi nibb Function Converts a long integer into ASCII string Syntax include lt stdlib h gt void ltoa_c31 long int val char dest int ndigits Prototype in stdlib h Remarks ltoa c31 converts a long integer number val into ASCII string dest containing exactly ndigits digits Return value None See also
70. s manual 59 http www spjsystems com character string pointer to character string char arg character No conversion is done the character is stored The optional type modifier character can be used with d I or u type characters when used it forces the scanf function to convert the input field into long int value instead of int so the corresponding address argument must be pointer to long int Return value Returns the last character written See also putchar Function Sends a byte to the on chip serial port Syntax include lt standard h gt void sendbyte unsigned char ch Prototype in standard h Remarks Sends the character ch to on chip serial port i e SBUF It also waits till the transmission is complete That is it will wait till the TI bit in SCON is set Before returning it clears the TI bit so that you are ready to send the next byte Return value None See also getbyte ser_rdy Function Checks the on chip serial port status Syntax include lt standard h gt int ser_rdy Prototype in standard h Remarks Checks whether a character is received on the on chip serial port Return value If a character is received returns non zero but the character remains in SBUF you may use getbyte to read it Otherwise returns zero See also getbyte SC51 User s manual 60 http www spjsystems com Function Sets the mode of serial port Syntax finclude lt macros
71. source program and compile again How can I see all of the error warning messages When you run the compiler it prints all of the warning and error messages on the Standard Output device i e generally the console If there are too many warnings errors you may not be able to see all of them on the screen In such a case you may use output redirection to catch all the warning error messages i e these can be saved in a file say SC51 ERR To do this invoke the compiler as shown below Sc51 options filename c gt sc51 err When you do this you will not see any warning error messages on the screen Instead these will go into the file sc51 err When the compile process is over you can view the file sc51 err using any text editor In most cases you will use the SIDE51 Integrated Development Environment In this case the error warning messages produced by the compiler assembler linker are displayed in the error window Warning Messages SC51 User s manual 79 http www spjsystems com Parameter paraname never used Where paraname is the name of a parameter This warning is usually displayed with a line number of the last line of a function in which the said parameter was defined Local variable localname declared but never used Where localname is the name of a local variable This warning is usually displayed with a line number of the last line of a function in which the said local var
72. ss of the memory model selected The keywords data idata bdata xdata pdata code can be used in a variable declaration to specify the memory area to be used for that variable Here are some examples xdata int j this will be stored in xdata memory area idata char ch idata memory area pdata char arr 10 pdata memory area data unsigned char uch data memory area SC51 User s manual 21 http www spjsystems com bdata char bch bdata memory area code float multipliers 3 1 0 2 0 3 0 code memory area long int DE default memory area The usage of memory area specifiers must follow some rules 1 Only one of these memory area specifiers maybe used data idata bdata xdata pdata code 2 Since code memory area is read only the variables declared with code memory area specifier can not be assigned any value The only way to assign a value to code variables is to initialize them during declaration as in the above example 3 Using the keyword const has exactly the same effect as using the code memory area specifier Although const is not a memory area name the use of const informs the compiler that this is a read only variable and hence compiler automatically keeps it in code memory area 4 The memory area specifier must be placed before the data type For example xdata int j is a valid variable declaration but int xdata j is not valid Generally the variable decla
73. t hi ex0 85 set hi ex 86 set hi ser 87 set hi to 88 set hi tl 89 set hi t2 90 set lo ex0 91 set lo exl 92 set lo ser 93 set lo tO 94 set lo tl 95 set lo t2 96 set tO mode 97 set t mode 98 set tcnt 99 sin 100 sinh 101 sprintf 102 sqrt 103 sscanf 104 start timer0 105 start_timerl 106 stop_timerO 107 stop_timerl 108 strcat 109 stremp 110 strcpy 11 1 strlen 112 strlwr 113 strncpy SC51 User s manual 29 http www spjsystems com 114 strupr 115 tan 116 tanh 117 tolower 118 toupper 119 ui2a_c31 120 ui2bcd SC51 User s manual 30 http www spjsystems com Function Returns the absolute value of an integer Syntax include lt stdlib h gt int abs int x Prototype in math h Remarks abs returns the absolute value of an integer argument x Return value abs returns an integer in the range of 0 to 32767 with the exception that an argument of 32768 is returned as 32768 See also labs Function Returns the arc cosine of the argument Syntax finclude lt math h gt float acos float x Prototype in math h Remarks This function is NOT included in the library but 1t is given in the form of source code It s source code can be found in SOURCE CFILES MATH C Return value acos returns the arc cosine of x See also cos Function Returns the arc sine of the argument Syntax include lt math h gt float asin float x Prototype in math h Remarks This function is NOT included
74. t may be sometimes very convenient to write small functions in assembly language and call these functions from C language program This section describes exactly how to do it Let us take a simple example it may not be useful in real life but it nonetheless illustrates the method to be followed This is how our example function goes _exmpl_func Example function written in assembly language mov a p0 read PO data rie a rotate left through Carry mov p0 a write back to PO ret In your C program you might call this function simply by writing exmpl_func Writing assembly language functions is as simple as that You only need to remember a few rules e An assembly language function must start with a label which is same as the name of the function preceded by an underscore character _ e This label name must be declared as PUBLIC for example PUBLIC _exmpl_func While calling such a function from C language program you must omit the underscore character e The assembly language function may modify the contents of any of the registers RO through R7 and Acc e Never switch register bank Never change the contents of Stack Pointer SP Make sure that the PUSHS and POPs are exactly matching e Never write into any location in internal or external data memory SC51 User s manual 74 http www spjsystems com e Never access any location in internal external data memory by using hardcoded addresse
75. the suffix it would have meant the int value 1237 Similarly the suffix UL can attached to a constant to force it to unsigned long int type Similarly the suffix S can attached to a constant to force it to unsigned char type For example 123S means the unsigned char value 123 a single byte value However without the S suffix 123 would have meant the int value 123 two bytes 3 7 Operators Following operators are supported by the compiler PS ole SC51 User s manual 15 http www spjsystems com Il Il Ve A Il V I I dl V Vv A A J amp N EE gt gt However on bit type variables some of the operators can not be used Here is the list of operators which can not be used with bit type variables gt gt lt lt lt lt gt gt 3 8 Function prototypes You may write function prototypes to declare a function These declarators include information about the function parameters e g int funcl char parl int par2 long int par3 The actual function definition may be written somewhere else as int funcl char parl int par2 long int par3 write some code her ees this is a valid function definition The old style of writing function definitions is NOT supported e g this is not allowed int funcl parl par2 par3 char parl
76. to execute but that time will not be counted by this function Thus if interrupts are enabled the acuracy and repeatability of this function will be poor Return value None Function Produces a delay Syntax include lt standard h gt void delay_ms int count Prototype in standard h SC51 User s manual 35 http www spjsystems com Remarks Produces a certain delay Since the crystal freguency in the target system is not known this function passes count 1000 number of clock cycles only Thus if you are using 8031 with 12 MHz crystal you may say that this function produces a delay of count milli seconds where count is the integer parameter you pass to it However if you are using a different crystal frequency and or different CPU it may not be so The accuracy of this function is plus or minus 2 cycles i e if you call delay function with count parameter 20 then it will return after n clock cycles where n will be gt 19998 and lt 20002 Also please note that this functions produces a software delay Thus if interrupts are enabled then this function may produce more delay than is expected Because if interrupt occurs during this function then it will take some more time to execute but that time will not be counted by this function Thus if interrupts are enabled the acuracy and repeatability of this function will be poor Return value None Function Disables interrupts Syntax includ
77. to the standard output device on chip serial port Syntax include lt stdio h gt char putchar char ch SC51 User s manual 57 http www spjsystems com Prototype in stdio h Remarks Sends the character ch to standard output device i e on chip serial port of 8051 i e SBUF It also waits till the transmission is complete That is it will wait till the TI bit in SCON is set Before returning it clears the TI bit so that you are ready to send the next byte Please note that as per conventions it checks whether the character being sent is Line Feed character Ox0a If so it also sends the Carriage Return character 0x0d to the standard output device The functions printf and puts call this function to send out each character The source code of this function in assembly language is available to the users The users may change this function as per their requirement so as to direct the standard output to something else rather than the serial port Return value Returns the character ch See also printf puts Function Sends a character string to standard output device Syntax include lt stdio h gt char puts char arr Prototype in stdio h Remarks Sends each character of the string arr to standard output device i e normally the on chip serial port until a null terminator character is found the null character is NOT output and then output a newline character Please note that it
78. ue read See also pokeb inportb Function Writes a byte to a memory location Syntax void pokeb int addr unsigned int value Prototype in standard h Remarks pokeb is a function that writes the byte given by value to the location in data memory whose address is specified by addr Actually the functions outportb and pokeb are exactly equivalent Return value None See also peekb outportb Function Computes x to the power of y Syntax include lt math h gt float pow float x float y Prototype in math h Remarks See exp SC51 User s manual 54 http www spjsystems com powerdown Function Puts the CPU in powerdown mode Syntax include lt macros31 h gt powerdown A Prototype in macros31 h Remarks Sets bit 1 of PCON so that the CPU goes to powerdown mode in which it consumes much less power Return value None See also go_idle Function Sends formatted output to the standard output device Syntax int printf char format Related Functions int sprintf char dest char format Prototype in stdio h Remarks The printf function sends formatted output to the standard output device which is the 8051 s on chip serial port in case of this compiler The sprintf function is same as printf function except it sends the output to the argument dest instead of to the standard output device The parameter format specifies how the output is to be formatted This paramete
79. urns 1 if c is a letter A Z or a z or a digit 0 9 Function Character classification function Syntax include lt ctype h gt bit isalpha char c Prototype in ctype h Remarks isalpha is a function that classifies ASCII coded integer values It returns 1 for true and 0 for false Return value isalpha returns 1 if c is a letter A Z or a z SC51 User s manual 48 http www spjsystems com isascii Function Character classification function Syntax include lt ctype h gt bit isascii char c Prototype in ctype h Remarks isascii is a function that classifies ASCII coded character values It returns 1 for true and O for false Return value isascii returns 1 if c is in the range 32 127 0x20 0x7F Function Character classification function Syntax finclude lt ctype h gt bit isdigit char Cc Prototype in ctype h Remarks isdigit is a function that classifies ASCII coded character values It returns 1 for true and O for false Return value isdigit returns 1 if c is a digit 0 9 Function Character classification function Syntax include lt ctype h gt bit islower char Cc Prototype in ctype h Remarks islower is a function that classifies ASCII coded character values It returns 1 for true and 0 for false Return value islower returns if c is a lower case letter a z Function Character classification function Syntax include lt ctype h gt SC51 User s manu
80. ut it in R2 inc ro mov a r0 read MSByte of parl mov r3 a p put TE irn R3 Note that lower byte at lower address philosophy or the little endian format is followed everywhere The remaining parameters are stored at consecutive locations backward e g par2 can be found at bp 5 Please note that you must never modify the contents of bp or sp 5 4 Calling C functions from assembly language You can simply call C language function from assembly language by name but by preceding it by an underscore character e g if your C function is defined as void some func You can call it from assembly language as lcall _some_func Please note it is also necessary to declare some func as an external symbol EXTRN CODE _some_func 5 4 1 Passing parameters If the C function takes any parameters you should make use of sp to pass parameters For example consider the function void some_func int parl unsigned char par2 LA SC51 User s manual 71 http www spjsystems com For simplicity let us assume that value of parl is in R3 R2 MSByte in R3 and value of par2 is in R4 The last parameter par2 in this case is pushed first i e parameters are pushed in the reverse sequence First you should push the parameters onto stack then you call the function then you should adjust the stack For the above example this is how you do it mov a r4 push acc par2 is pushed mov a r2 push acc
81. value None See also set hi ser Function Sets low priority for timer 0 interrupt Syntax finclude lt macros31 h gt set lo t0 A Prototype in macros31 h Remarks Clears bit 1 of IP so that timer 0 interrupt gets a low priority Return value None See also set hi 0 SC51 User s manual 64 http www spjsystems com set lo t1 Function Sets low priority for timer 1 interrupt Syntax finclude lt macros31 h gt set lo t1 Prototype in macros31 h Remarks Clears bit 3 of IP so that timer 1 interrupt gets a low priority Return value None See also set_hi_tl Function Sets low priority for timer 2 interrupt Syntax finclude lt macros31 h gt set lo t2 3 Prototype in macros31 h Remarks Clears bit 5 of IP so that timer 2 interrupt gets a low priority Return value None See also set hi t2 Function Sets timer 0 mode Syntax finclude lt macros31 h gt set_t0_mode gate c_t mode Prototype in macros31 h Remarks This function writes the appropriate byte in TMOD If gate is 1 then the GATE bit in TMOD for Timer 0 will be set otherwise it will be cleared If c_t is 1 then Timer O will be used as a counter otherwise it will be used as a timer mode can be either 0 1 2 or 3 Return value None See also set t1 mode SC51 User s manual 65 http www spjsystems com set t1 mode Function Sets timer 1 mode Syntax finclude lt macros31 h gt set_t1_mode gate c_t mode

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