1. LHO 22 C and the 8051

2.  The Silicon Labs ISE uses the Keil C51 compiler.  The code size is limiter to 2K  C has replaced PL/M (the original Intel high level language (HLL) for imbedded systems).  Versions of basic and a few other HLL such as FOUTH are available for the 8051.  The Keil C51 is a complete implementation of ANSI C with extensions. o The extensions support various features of the 8051. o See Chapter 3 of the C51 compiler manual. You can find this using the Help menu.

3. Assembly Code Object Code Assembler C Code Object Code Linker Machine Code Compiler Code Generation Flow for assembler and C.

4. Include c8051F020.h in each C file. c8051F020.h defines the special function registers (SFR) of the 8051F020. /* BYTE Registers */ sfr P0 = 0x80;/* PORT 0 */ sfr SP = 0x81;/* STACK POINTER */ sfr DPL = 0x82;/* DATA POINTER - LOW BYTE */ sfr DPH = 0x83;/* DATA POINTER - HIGH BYTE */ sfr P4 = 0x84; /* PORT 4 */ … /* BIT Registers */ /* TCON 0x88 */ sbit TF1 = TCON ^ 7; /* TIMER 1 OVERFLOW FLAG */ sbit TR1 = TCON ^ 6; /* TIMER 1 ON/OFF CONTROL */

5. uni.c ;Version 1.1 11/29/07 #include // SFR declarations #include //---------------------------------------------------------------- // Init - Configure UDC // Returns : None // Parameters : None //---------------------------------------------------------------- void init_crossbar(void); void init_ports(void); void init_osc(void);

6. void Init (void) { // Disable interrupts EA = 0; // Disable watchdog timer WDTCN = 0xde; WDTCN = 0xad; init_osc(); // Enable crossbar switch init_crossbar(); // Set up ports init_ports(); }

7. //------------------------------------------------------------------ // rd_buttons - Configure IO ports // Returns : Value of buttons connected to P5.3 - P5.0. // Pressing a button // sets bit to a '1'. // Parameters : None //------------------------------------------------------------------ unsigned char rd_buttons(void) { unsigned char btns; btns = (~P5) & 0x0f; return(btns); }

8. //------------------------------------------------------------------ // wr_leds - Outsput to led's // Returns : None // Parameters : leds //------------------------------------------------------------------ void wr_leds(unsigned char leds) { P5 = (leds << 4) | 0x0f; }

9. //------------------------------------------------------------------ // init_ports - Configure IO ports // Returns : None // Parameters : None //------------------------------------------------------------------ void init_ports(void) { P0MDOUT = 0x00; P1MDOUT = 0x00; P2MDOUT = 0x00; P3MDOUT = 0x00; P5 = 0x0f; //TURN ON LEDS P74OUT = 0x08; // SET PORT 5 OUT AS PUSH PULL P4 = 0xff; ; }

10. //----------------------------------------------------------------- // Init_crosbar - Configure crossbar switch // Returns : None // Parameters : None //----------------------------------------------------------------- void init_crossbar (void) { XBR0 = 0x0; XBR1 = 0x0; XBR2 = 0x48; // Enable cross bar }

11. //------------------------------------------------------------------ // init_osc - Use external 22.1184 XTAL as clock // Returns : None // Parameters : None //------------------------------------------------------------------ void init_osc (void) { OSCXCN = 0x67; //enable 22.1184 MHz XTAL OSC while ((OSCXCN & 0x80) == 0); // Wait till XTLVLD // pin is set See Fig 14.3 OSCICN = 0x88; //config internal oscillator }

12. //----------------------------------------------------------------- // delay - delay for visiable blink // Returns : None // Parameters : None //----------------------------------------------------------------- void delay(void) { unsigned int x; unsigned char y; while(x++) { y = 10; while(y--); }

17.  External data memory, up to 64 kB, can be read from and written to and is physically located externally from the CPU  Access to external data in XDATA space is very slow when compared to access to internal data  This is because external data memory is accessed indirectly through the data pointer register (DPTR) which must be loaded with a 16-bit address before accessing the external memory  There are two different data types in Cx51 used to access external data: xdata and pdata  The xdata memory specifier refers to any location in the 64 kB address space of external data memory (default for LARGE memory model)  The pdata memory type specifier refers to only 1 page or 256 bytes of external data memory (default for COMPACT memory model)  The pdata area is accessed using registers R0 and R1 indirectly (@R0 or @R1) instead of the DPTR (@DPTR), so accessing pdata is slightly faster than xdata. This is also what limits pdata to 256 bytes (R0 and R1 are 8 bits).

18.  Arithmetic operators perform basic arithmetic operations  All arithmetic operators except the negation (–) operator have two operands.  The negation (unary minus) operator returns the 2’s complement value of the operand  This is especially useful to specify a count that will be counted up rather than counted down  Example: unsigned int count = 0x0F; // TMR2RL gets 0xFFFF-0x0F+1 = 0xFFF1 TMR2RL = -count; OperatorDescription +Add –Subtract *Multiply /Divide %Modulo (remainder of division) –Negation (unary minus)

19.  Relational operators compare data and the outcome is either True or False  if statements, for loops and while loops often make use of relational operators OperatorDescription ==Equal to !=Not Equal to <Less than >Greater than <=Less than or equal to >=Greater than or equal to

20.  Logical operators operate on Boolean data (True and False values) and the outcome is also Boolean OperatorDescription &&Logical AND ||Logical OR !Logical NOT

21.  The C language also has several bitwise operators  Bitwise operators affect a variable on a bit-by-bit basis  Example: Result = Value1 & Value2;  If Value1 = 00100100b and Value2 = 10100000b, the result of Value1 & Value2 is: 00100100b & 10100000b = 00100000b OperatorDescription &Bitwise AND |Bitwise OR ~Bitwise NOT (1’s Compliment) ^Bitwise Exclusive OR <<Shift Left >>Shift Right

22.  Turning Bits On  Turn on a particular bit by ORing with a 1  Turning Bits Off  Turn off a particular bit by ANDing with a 0  Toggling Bits  Turning a bit from off to on or on to off by EXCLUSIVELY ORing with a 1 Bit wise Operators