The modules in this lab room are 4 line by 16 character display modules. The data sheet/users manual for the module is posted on My.Seneca.

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1 LCD Modules A common output display device used with low cost embedded systems is a character LCD display. The displays are available as complete modules with a standard microprocessor parallel interface. These displays come in sizes of 1 4 lines and 8 40 characters per line. The characters are displayed using a 5x7 dot matrix format. The modules in this lab room are 4 line by 16 character display modules. The data sheet/users manual for the module is posted on My.Seneca. LCD Module Features 4 line by 16 characters 5x7 or 5x10 dot matrix characters 4 or 8 bit parallel interface 80 character display memory 160 character ROM generator for 5x7 dot characters 32 character ROM generator for 5x10 dot characters 8 character RAM generator for 5x7 dot characters LCD Module interface D[7..0] RS R/W E CONTRAST_ADJ BACKLITE data bus register select read/write device select active HIGH LCD Registers RS R/W Description 1 1 Read data 1 0 Write data 0 1 Read status 0 0 Write instruction Interface Timing Item Symbol Min Typ Max Unit E Cycle Time tc ns E Rise/Fall Time t R, t F E Pulse Width (High, Low) t W R/W and RS Setup Time t su R/W and RS Hold Time t H Data Setup Time t su Data Hold Time t H G VandeBelt

2 Write Timing RS th1 tsu1 R/W tw th1 tf E tf tsu2 th2 DB0-DB7 Valid Data tc Item Symbol Min Typ Max Unit Data Setup Time t su ns Data Hold Time t H ns Read Timing RS tsu th R/W tw th tf E tf td tdh DB0-DB7 Valid Data tc Item Symbol Min Typ Max Unit Data Output Delay Time t D ns Data Hold Time t DH ns G VandeBelt

3 Character addressing The two digit hex number in the is the memory address in the LCD module which contains the character to be display at the line column location. Module Instructions Display Mode Cursor control Clear display Cursor addressing Character RAM addressing See next page for list of instructions Module Reset The module is normally reset on power on. However if the power up time is slow, the module may not reset properly and so a special sequence is required to ensure the module is reset and configured to the correct operating mode. This is important since the data bus can be configured for 4 or 8 bit wide operation. The diagram on page 5 describes the power on reset procedure for 8 bit operation. Write Operation All instructions require a specified length of time to complete as listed in the following chart. No new instructions can be issued while the module is processing an instruction. During this time the BF flag will be set. There are two methods which can be used to ensure that the previous instruction is completed before issuing another instruction: 1) test the BF bit and wait until cleared 2) wait for the required interval. G VandeBelt

4 Instruction Set Instruction Instruction Code Description Execution Time (fosc= 270kHz) RS R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 Clear Write 20H to DDRAM, and set 1.53ms Display DDRAM address to 00H from AC. Return X Set DDRAM address to 00H from AC 1.53ms Home and return cursor to its original position if shifted. The contents of DDRAM are not changed. Entry Mode I/D S Assign cursor moving direction. 39us Set I/D= 1 : increment, I/D= 0 : decrement and display shift enable bit. S= 1 : make entire display shift of all lines during DDRAM write. S= 0 : display shift disable Display ON/OFF Control D C B Set display/cursor/blink on/off D= 1 : display on, D= 0 : display off, C= 1 : cursor on, C= 0 : cursor off, B= 1 : blink on, B= 0 : blink off. 39us Cursor or Display Shift S/C R/L X X Cursor or display shift, S/C= 1 : display shift, S/C= 0 : cursor shift, R/L= 1 : shift to right, R/L= 0 : shift to left. 39us Function Set DL N F X X Set interface data length DL= 1 : 8-bit DL= 0 : 4-bit N= 1 : 2-line display N= 0 : 1-line.display F= 0 5*7-dot F= 1 5*10-dot 39us Set CGRAM Address AC5 AC4 AC3 AC2 AC1 AC0 Set CGRAM address in address counter 39us Set DDRAM Address AC6 AC5 AC4 AC3 AC2 AC1 AC0 Set DDRAM address in address counter 39us Read Busy Flag and Address 0 1 BF AC6 AC5 AC4 AC3 AC2 AC1 AC0 Can be known whether during internal operation or not by reading BF. The contents of address counter can also be read. BF= 1 : busy state, BF= 0 : ready state. Write Data 1 0 D7 D6 D5 D4 D3 D2 D1 D0 Write data into internal RAM (DDRAM/CGRAM). Read Data 1 1 D7 D6 D5 D4 D3 D2 D1 D0 Read data from internal RAM (DDRAM/CGRAM) 0us 43us 43us G VandeBelt

5 LCD Initialization sequence G VandeBelt

6 Lab Configuration The lab hardware has the module data bus connected to PORT B and the three control lines driven from PORT K. Signal Port Pin Comments D0 D7 PORT B 0-7 Shared with LEDs E PORT K.0 R/W PORT K.1 RS PORT K.2 Note that PORT B also drives the LEDs. As a result, if the LEDs are used in the code you can not read from the module. When writing to the module, the data for the LEDs must be saved before the LCD write and restored after the write is complete. If your code requires read access to the LCD module, the LEDs must be disabled. In the lab we will not use read operations. Since the BF flag can not be tested, we will time the access to the module. LCD Driver Design To simplify use of the LCD module we will design a driver which will provide a simple interface between the LCD and the application software. The application interface will consist of four functions: 1) module initialization LCDopen() 2) write a data character LCDputch() 3) write string LCDputs() 4) write an instruction. LCDinstruct() Data is written to the output as ASCII characters. The LCD driver is interrupt driven. Timer Channel 6 is used in Output Compare mode. A single character or instruction is written to the module on every interrupt. After command, the timer is set to interrupt after the time required for the command to be processed. When all information has been output to the LCD, the timer interrupt is disabled. When the application writes to the LCD driver, the output function stores the write data in a FIFO (First in/first out queue) and enables the Timer interrupt. When the timer interrupt occurs, the FIFO is checked for data. If it is empty, the timer interrupt is disabled. If the FIFO is not empty, the next data in the FIFO is written to the LCD module and the timer is set to interrupt after the time required for the command to be processed. To handle instructions (clear, cursor position, etc), an escape sequence is used. All instructions are preceded by an special escape character. In the interrupt routine, the software checks for this character. If found, the character is discarded and the next character in the FIFO is treated as an instruction instead of data. G VandeBelt

7 Initialization Function static void initcmd(unsigned char cmd, unsigned int delay); LCDopen Initialize the LCD display following a power on reset. The algorithm is taken from the OPTREX User's Manual. void LCDopen(void) set up Port K for LCD controls set direction to output DDRK_DDK0 = 1; DDRK_DDK1 = 1; DDRK_DDK2 = 1; default output data LcdRnW = 0; LcdRS = 0; LcdEN = 0; default to write default to instruction EN low LCDput = LCDbuf; LCDtake = LCDbuf; FIFO pointers set up Timer channel 6 for compare mode TIOS = 0x40; /* select Timer 6 for output compare */ TCTL1 &= ~0x30; /* timer 6 disconnected from PORT T pin6 */ implement the algorithm 1) ensure 15 ms delay after power-on TC6 = TCNT + DLY15ms; TFLG1 = 0x40; /* clear interrupt flag for C6 by writing a 1 */ 2) function set command: 4.1 ms delay - use 5 ms initcmd(lcdcfg, DLY5ms); 3) function set command: 100 us delay initcmd(lcdcfg, DLY100us); 4) function set command: 80 us delay initcmd(lcdcfg, DLY80us); LCD reset complete - now configure the LCD interface width initcmd(lcdcfg, DLY80us); we can now use the normal LCD commands to complete the configuration LCDinstruct(LCDcfg); the real function set LCDinstruct(LCDdsplyOFF); display OFF LCDclear(); clear display LCDinstruct(LCDmode); set mode LCDinstruct(LCDcursorON); display ON - cursor ON G VandeBelt

8 Instruction write to LCD module during initialization cmd : instruction to write delay : instruction processing time static void initcmd(unsigned char cmd, unsigned int delay) unsigned char PORTdata; while (!(TFLG1&0x40)) ; wait for previous command to complete PORTdata = PORTB; PORTB = cmd; LcdEN = 1; LcdEN = 0; TC6 = TCNT + delay; TFLG1 = 0x40; PORTB = PORTdata; save LED status - Port B shared with LEDs output the command EN set HIGH EN is now LOW set the instruction execution time clear time-out flag restore LED status Useful Defines contained in LCD.H #define LCDdsplyOFF 0x08 display OFF command #define LCDdsplyON 0x0C display ON, cursor OFF #define LCDcursorOFF 0x0C display ON, cursor OFF #define LCDcursorON 0x0E display ON, cursor ON #define LCDblink 0x0F display ON, cursor blink #define LCDshiftR 0x14 shift cursor right #define LCDshiftL 0x10 shift cursor left #define LCDputch(x) LCDputByte(x, 0) write data character #define LCDinstruct(x) LCDputByte(x, 1) write instruction #define LCDclear() LCDputByte(0x01, 1) clear display #define LCDhome() LCDputByte(0x02, 1) move cursor to home position #define LCDline1() LCDputByte(0x80, 1) move cursor to start of line 1 #define LCDline2() LCDputByte(0xC0, 1) move cursor to start of line 2 #define LCDline3() LCDputByte(0x90, 1) move cursor to start of line 3 #define LCDline4() LCDputByte(0xD0, 1) move cursor to start of line 4 LCD Memory #define LCDsize 128 unsigned char *LCDput; FIFO write pointer unsigned char *LCDtake; FIFO read pointer unsigned char LCDbuf[LCDsize]; the FIFO #define LCDend (LCDbuf+LCDsize-1) FIFO wrap address G VandeBelt

9 User Commands LCDputByte This function sends a byte to the LCD. The "type" defines the data as instruction or display character Procedure: 1) if type is non-zero, insert 0xFE into FIFO to signal instruction 2) insert data into FIFO 3) advance FIFO pointer 4) enable Timer interrupt void LCDputByte(unsigned char data, unsigned char type) unsigned char *ptr; write FIFO pointer ptr = LCDput; working copy of FIFO pointer if (type) instruction for LCD display *ptr = 0xFE; flag instruction if (ptr == LCDend) ptr = LCDbuf; queue wrap else ptr++; if (ptr == LCDtake) return; FIFO is full - discard data *ptr = data; send data if (ptr == LCDend) ptr = LCDbuf; queue wrap else ptr++; if (ptr == LCDtake) return; FIFO is full - discard data LCDput = ptr; update FIFO pointer TIE = 0x40; ensure interrupts are enabled LCDputs This function outputs a NULL terminated string to the LCD display. The function does NOT handle line wrapping. void LCDputs(const char *s) for ( ;*s!= 0; s++) LCDputch(*s); G VandeBelt

10 Interrupt Routine /* Timer interrupt routine for LCD. */ interrupt void LCDisr(void) unsigned char data; unsigned char PORTdata; temporary storage for LED status first check for more data to display if (LCDtake == LCDput) FIFO is empty disable interrupts but DON'T clear the flag TIE &= ~0x40; LCD inactive return; data = *LCDtake; get data if (data == 0xFE) this is an instruction if (LCDtake == LCDend) LCDtake = LCDbuf; handle wrapping else LCDtake++; data =*LCDtake; get instruction LcdRS = 0; else LcdRS = 1; data address PORTdata = PORTB; PORTB = data; LcdEN = 1; LcdEN = 0; PORTB = PORTdata; save LED status output the byte EN set HIGH EN is now LOW restore LED status start the delay timer if ((LcdRS == 0) && (data < 4)) CLEAR or HOME instruction TC6 = TCNT + DLY3ms; else TC6 = TCNT + DLY80us; TFLG1 = 0x40; clear interrupt flag if (LCDtake == LCDend) LCDtake = LCDbuf; handle wrapping else LCDtake++; G VandeBelt

11 Example /* Sample code to demonstrate the use of the LCD driver. The program reads the DIP switches on PORT H and writes information to the LCD module. Switch Pattern OFF OFF OFF OFF OFF OFF OFF OFF : clear screen OFF OFF OFF OFF OFF OFF OFF ON : Write to line 1 OFF OFF OFF OFF OFF OFF ON OFF : Write to line 2 OFF OFF OFF OFF OFF OFF ON ON : Write to line 3 OFF OFF OFF OFF OFF ON OFF OFF : Write to line 4 All other patterns have no effect */ #include <hidef.h> /* common defines and macros */ #include < mc9s12dp256.h > /* derivative information */ #include "lcd.h" header file containing defines & prototypes void main(void) unsigned char code, prev; unsigned int x; DDRB = 0xFF; PORTB = 0xFF; DDRH=0x00; PERH=0xFF; PORTB is output for LEDs and LCD data PORTH as input add pull up resistors to PORTH Timer system used by LCD and others - 1 us resolution TSCR2 = 0x03; prescale by 8-1 MHz clock TSCR1 = 0x80; enable timer LCDopen(); initialize the LCD driver EnableInterrupts; prev = 0xFF; while(1) /* do forever */ code = ~PTH; get switch pattern if (code!= prev) check for switch change if (code == 0x00) check for all OFF LCDclear(); else if (code ==0x01) identify other patterns LCDhome(); move to line 1 and display LCDputs("Line 1"); else if (code ==0x02) LCDline2(); move to line 2 and display LCDputs("Second line"); else if (code ==0x03) LCDline3(); move to line 3 and display LCDputs("Third line"); else if (code ==0x04) LCDline4(); move to line 4 and display LCDputs("Last line"); prev = code; while ((TFLG2 & 0x80) == 0) ; delay to slow down operation TFLG2 = 0x80; clear timer overflow flag G VandeBelt