;**************************************************************************** ; Test program for LCD 4-bits interface routines ; ; Also, this file can be used as an skeleton to develop an application ; using an LCD display module. ; ; If interrupts are not used all code presented between the ORG ; 0x004 directive and the label main can be removed. In addition ; the variable assignments for 'w_temp' and 'status_temp' can ; be removed. ; ;**************************************************************************** ; list p=16F84 ; list directive to define processor #include ; processor specific variable definitions __CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _RC_OSC ; '__CONFIG' directive is used to embed configuration data within .asm file. ; The lables following the directive are located in the P16F84X.INC file. The ; following values are possible: ; ; _CP_ON Code Protection ON ; _CP_OFF Code Protection OFF ; ; _PWRTE_ON Power-Up Timer Enable Bit ON ; _PWRTE_OFF Power-Up Timer Enable Bit ON ; ; _WDT_ON Watch Dog Timer ON ; _WDT_OFF Watch Dog Timer OFF ; ; _LP_OSC Low Power crystal oscillator (32Khz-200Khz) ; _XT_OSC XT crystal oscillator (100Khz-4MHz) ; _HS_OSC HS crystal oscillator (4Mhz-10Mhz) ; _RC_OSC RC oscillator ;**************************************************************************** ; Definitions for variables allocated in internal RAM ;**************************************************************************** ; Context saving when entering into de Interrupt Service routine ;---------------------------------------------------------------------------- ; #define USE_ISR ; un-comment this definition if interrupts are used ifdef USE_ISR cblock 0x10 w_temp ; variable used for context saving status_temp ; variable used for context saving endc else cblock 0x10 endc endif ; LCD module ;---------------------------------------------------------------------------- ; LCD presentation atributes: #define DISPLAY_ON 0x04 | 0x08 ; Display ON #define CURSOR_ON 0x02 | 0x08 ; Cursor ON #define BLINKING_ON 0x01 | 0x08 ; Blink character at cursor position ; LCD variables: cblock LCD_aux ; nibble to write is kept in low nibble of this byte LCD_addr ; current address LCD_saveW ; to save W LCD_char ; char to write to LCD (used only by WriteChar, putc) endc ; Variables for the timming routines (Wait_Wx1ms, Wait_Wx100us, Wait_Wx10us) ;---------------------------------------------------------------------------- cblock nWaitTime nWaitT2 nWaitT3 endc cblock nAux1 endc ;**************************************************************************** ; Data in EEPROM ;**************************************************************************** ; de "Probando esto.",0 ;**************************************************************************** ; Program code starts here ;**************************************************************************** Reset: org 0x000 ; processor reset vector goto Start ; go to beginning of program ;**************************************************************************** ; Interrupt Service Routine (ISR) ;**************************************************************************** ISR: org 0x004 ; interrupt vector location ifndef USE_ISR goto Start else movwf w_temp ; save off current W register contents movf STATUS,w ; move status register into W register movwf status_temp ; save off contents of STATUS register ; isr code can go here or be located as a call subroutine elsewhere movf status_temp,w ; retrieve copy of STATUS register movwf STATUS ; restore pre-isr STATUS register contents swapf w_temp,f swapf w_temp,w ; restore pre-isr W register contents retfie ; return from interrupt endif ;**************************************************************************** ; Reset code starts here ;**************************************************************************** Start: ; initialize port b: all lines are outputs with weak pull-up clrf portb ; output data latches to 0 bsf status,rp0 ; select bank 1 bcf option_reg,not_rbpu ; enable weak pull-up resistors clrf trisb ; all lines as outputs bcf status,rp0 ; select bank 0 ;**************************************************************************** ; Main program loop starts here ;**************************************************************************** Main: ; Test basic routines ; call LCD_Initialize movlw 'H' call LCD_SendData ;1 movlw 'o' call LCD_SendData ;2 movlw 'l' call LCD_SendData ;3 movlw 'a' call LCD_SendData ;4 movlw ',' call LCD_SendData ;5 movlw ' ' call LCD_SendData ;6 movlw 'D' call LCD_SendData ;7 movlw 'o' call LCD_SendData ;8 movlw 0x0c0 ; set address call LCD_SendCmd movlw 'r' call LCD_SendData ;1 movlw 'i' call LCD_SendData ;2 movlw 'n' call LCD_SendData ;3 movlw 'd' call LCD_SendData ;4 movlw 'a' call LCD_SendData ;5 movlw ' ' call LCD_SendData ;6 movlw '3' call LCD_SendData ;7 movlw '.' call LCD_SendData ;8 ; Test LCD_Home and logical addressing routines call wait_5secs call LCD_Home movlw 'E' call LCD_putc ;1 movlw 's' call LCD_putc ;2 movlw 't' call LCD_putc ;3 movlw 'o' call LCD_putc ;4 movlw ' ' call LCD_putc ;5 movlw 'e' call LCD_putc ;6 movlw 's' call LCD_putc ;7 movlw ' ' call LCD_putc ;8 movlw 'u' call LCD_putc ;9 movlw 'n' call LCD_putc ;10 movlw 'a' call LCD_putc ;11 movlw ' ' call LCD_putc ;12 movlw 'p' call LCD_putc ;13 movlw 'r' call LCD_putc ;14 movlw 'u' call LCD_putc ;15 movlw 'e' call LCD_putc ;16 loop2: ; RB0 --> LED + 470 ohm --> gnd bsf portb,0 ; LED ON for 500ms movlw 250 call Wait_Wx1ms movlw 250 call Wait_Wx1ms bcf portb,0 ; LED OFF for 500ms movlw 250 call Wait_Wx1ms movlw 250 call Wait_Wx1ms goto loop2 wait_5secs: movlw 20 ; wait 5 secs = 20x250ms movwf nAux1 loop1: movlw 250 call Wait_Wx1ms decfsz nAux1,f goto loop1 return ;**************************************************************************** ;**************************************************************************** ;** Subroutines start here ;**************************************************************************** ;**************************************************************************** ;**************************************************************************** ; 4-bit LCD control routines for the PIC16F84 ; ; This routines are intended to control an LCD display built around the ; HD44780 Hitachi controller, or compatible, using only one ; controller chip (typically 1x16, 1x20, 2x16 or 2x20 displays). The ; HD44780 is very common and widely used by most display makers. ; ; C.Salmeron 27/Mar/99 ; ;---------------------------------------------------------------------------- ; USAGE: ;---------------------------------------------------------------------------- ; STEP 1. Un-comment the following definitions and code block and move it ; to the begining of the program, at an appropiate place. ; ;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ;; LCD presentation atributes: ; ;#define DISPLAY_ON 0x04 | 0x08 ; Display ON ;#define CURSOR_ON 0x02 | 0x08 ; Cursor ON ;#define BLINKING_ON 0x01 | 0x08 ; Blink character at cursor position ; ;; LCD variables: ; ; cblock ; LCD_aux ; the nibble to write is kept in low nibble of this byte ; LCD_addr ; cursor position (physical address) ; LCD_saveW ; to save W ; endc ;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ;---------------------------------------------------------------------------- ; STEP 2: LCD Configuration ; ; It is assumed that LCD is conected to port B as follows: ; D7 -> RB7 ; D6 -> RB6 ; D5 -> RB5 ; D4 -> RB4 ; RS -> RB3 ; RW -> RB2 ; E -> RB1 ; ; If you desire to change the above described configuration, take into ; account that data lines D7-D4 must be assigned to a nibble of a PIC16F84 ; port, either the high nibble of PORTB (RB7-RB4) or the low nibble of ; either porta (RA3-RA0) or portb (RB3-RB0). D7 must be assigned to the ; most significative bit of the chosen port nibble. ; If the configuration is changed, change the following definitions ; as appropiate (it is not necessary to move this code to another part of ; the program): ; ioLCD_E equ 1 ;port bit assigned to LCD control line E ioLCD_RW equ 2 ;port bit assigned to LCD control line RW ioLCD_RS equ 3 ;port bit assigned to LCD control line RS ioLCD_D7 equ 7 ;port bit assigned to LCD data line D7 #define port_E portb ;port used for LCD control line E #define port_RW portb ;port used for LCD control line RW #define port_RS portb ;port used for LCD control line RS #define port_LCD portb ;port used for LCD data lines #define tris_LCD trisb ;tris register for LCD data lines #define ioMaskW 00000000b ;mask to program LCD data port to write to LCD ; 0 = all RBx io pins are outputs #define ioMaskR 11110000b ;mask to program LCD data port to read from LCD ; 1 = io pins RB7-RB4 are inputs #define LCD_lines 1 ; display type: 1 line or 2 lines ;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ;-- ONLY FOR MY EYES -------------------------------------------------------- ; ; My LCD moule is wired as follows: ; ; 14 [Cinta plana-gris] (D7) ; ... ... ; 8 [Cinta plana-gris] (D1) - pines no usados: dejar al aire ; 7 [Cinta plana-azul] (D0) ; 6 [Naranja] (E) ; 5 [Verde] (R/W) ; 4 [Amarillo] (RS) ; 3 [Azul] (Vo) = Cursor de potenciometro 10K entre +5 y 0v/-5v ; 2 [Rojo] (Vdd) = +5v ; 1 [Negro] (Vss) = 0v ; ;---------------------------------------------------------------------------- ; STEP 3 (and last): Optional ; To save program space, remove the LCD routines not used by you app. ; ; The following routines are available: ; ; a) Low level functions. (All necessary. Do not remove any of them): ; iLCD_WaitReady // wait until LCD module not busy ; iLCD_SendByte // Send to LCD the byte (data or command) received in W ; ; b) Basic functions (All necessary. Do not remove any of them): ; LCD_SendData // Write to LCD the data byte received in W ; uses: iLCD_SendByte, iLCD_WaitReady ; LCD_SendCmd // Send a command to LCD ; uses: iLCD_WaitReady, iLCD_SendByte ; LCD_Initialize // Inicialize LCD. MUST BE THE FIRST FUNCTION TO CALL ; Uses: LCD_SendCmd ; ; c) Additional functions (remove any not needed in your app.): ; LCD_CleanUp // Clear display and move cursor to home position ; LCD_CursorLeft // Shift cursor one position to the left ; LCD_CursorRight // Shift cursor one position to the right ; LCD_Home // Move cursor and display window to home position ; LCD_SetDataAddr // Set address for data write (DD RAM) ; LCD_GetAddr // Return current address ; LCD_putc // Write char to current address. ; LCD_WriteChar // escribir char en posic indicada ; LCD_puts // write string *dptr to current cursor position ; LCD_putns // write string *sp to current cursor position ; ;**************************************************************************** ;=========================================================================== ;=========================================================================== ;; a) Internal functions. All needed ;=========================================================================== ;=========================================================================== ;---------------------------------------------------------------------------- ; iLCD_WaitReady (LWR) ; Wait until LCD is not busy. ;---------------------------------------------------------------------------- iLCD_WaitReady: movwf LCD_saveW ; save w ; set all data lines as inputs bsf status,rp0 ; select bank 1 movlw ioMaskR ; mask to set LCD data lines as inputs movwf tris_LCD ; use mask in W to program port bcf status,rp0 ; select bank 0 bcf port_RS,ioLCD_RS ; RS=0 signal it is a command bsf port_RW,ioLCD_RW ; R/W=1 signal it is a read operation nop ; wait 1us to comply with timming requirements LWR_IsBusy?: bsf port_E,ioLCD_E ; E=1 enable LCD nop ; wait 1us to comply with timming requirements movf port_LCD,w ; read data lines movwf LCD_aux ; and save bcf port_E,ioLCD_E ; E=0 disable LCD btfss LCD_aux,ioLCD_D7 ; test busy line. goto LWR_NotBusy ; jump if LCD not busy ; LCD is busy. Read the low order nibble and ignore it bsf port_E,ioLCD_E ; E=1 enable LCD nop ; wait 1us to comply with timming requirements bcf port_E,ioLCD_E ; E=0 disable LCD goto LWR_IsBusy? ; loop ; LCD is not busy. Read and ignore low nibble, and return LWR_NotBusy: bsf port_E,ioLCD_E ; E=1 enable LCD nop ; wait 1us to comply with timming requirements bcf port_E,ioLCD_E ; E=0 disable LCD ; reprogram all LCD data lines as outputs bsf status,rp0 ; select bank 1 movlw ioMaskW ; mask to set LCD data lines as outputs movwf tris_LCD ; program port bcf status,rp0 ; select bank 0 movf LCD_saveW,w ; restore w return ;---------------------------------------------------------------------------- ; iLCD_SendByte (LSB) ; Send to LCD the byte (data or command) received in W. It is assumed ; that lines RS and RW have been properly set before calling this function. ; ; As it is a 4-bits interface, data is sent as two nibbles, one nibble ; at a time. ;---------------------------------------------------------------------------- iLCD_SendByte: ; high nibble must be sent first movwf LCD_saveW ; save byte to send movwf LCD_aux ; high nibble of byte to send is moved to .. swapf LCD_aux,f ; .. low nibble of LCD_aux call LSB_WriteNibble ; send low nibble of LCD_aux ; now prepare and send low nibble movf LCD_saveW,w ; retrieve byte to send movwf LCD_aux ; move it to LCD_aux ; goto LSB_WriteNibble ; send low nibble of LCD_aux ; Send the low nibble of LCD_aux to LCD LSB_WriteNibble: bsf port_E,ioLCD_E ; E=1 enable LCD movlw 0x0f andwf LCD_aux,f ; high nibble of data to zeros if ioLCD_D7 == 7 ; if D7-D4 conected to high nibble of PIC port andwf port_LCD,f ; clear high nibble of port (data lines D7-D4) swapf LCD_aux,f ; move data to send to high nibble else ; else if D7-D4 conected to low nibble movlw 0x0f0 andwf port_LCD,f ; clear low nibble of port (data lines D3-D0) endif movf LCD_aux,w ; move data to W iorwf port_LCD,f ; write data to port nop bcf port_E,ioLCD_E ; E=0. LCD reads data when falling edge of E movlw 5 ; wait 50 uS for LCD internal process goto Wait_Wx10us ;=========================================================================== ;=========================================================================== ;; b) Basic functions. All needed ;=========================================================================== ;=========================================================================== ;---------------------------------------------------------------------------- ; LCD_SendData ; Write to LCD the data byte received in W. After write, the address is ; incremented or decremented by one, according to the entry mode ;---------------------------------------------------------------------------- LCD_SendData: call iLCD_WaitReady ; wait until LCD not bussy bcf port_RW,ioLCD_RW ; R/W=0 signal it is a write operation bsf port_RS,ioLCD_RS ; RS=1 signal it is a data byte goto iLCD_SendByte ;---------------------------------------------------------------------------- ; LCD_SendCmd ; Send to LCD the command byte received in W ; ; LCD_SetDataAddr ; Set address for data write to the address specified in W ; (line 1: 80h-A7h) or (line 2: C0h-E7h). Note that changing the address ; is just sending the address as a command: bit 7 to one is the command ; "set address" ;--------------------------------------------------------------------------- LCD_SetDataAddr: LCD_SendCmd: call iLCD_WaitReady ; wait until LCD not bussy bcf port_RW,ioLCD_RW ; R/W=0 signal it is a write operation bcf port_RS,ioLCD_RS ; RS=0 signal it is a command byte goto iLCD_SendByte ;---------------------------------------------------------------------------- ; LCD_Initialize ; At power on, if power supply raises from 0v to 4.5v in less than 10mS ; but not faster than 1mS, the LCD module will default to the following ; settings: ; 1. Clear display ; 2. 8-bits interface, 1 line display, 5x7 dot font ; 3. Display OFF, Cursor ON, Blink OFF ; 4. Entry mode: increment, no display shift ; 5. DD RAM is selected ; ; Whether the LCD is initialized or not, this function (LCD_Initialize) ; will change the LCD module to the following settings: ; 1. Clear display ; 2. 4-bits interface, 2 lines display, 5x7 dot font ; 3. Display ON, Cursor ON, Blink OFF ; 4. Entry mode: increment, no display shift ; 5. DD RAM is selected ; ; For other settings at initialization time, change this routine. ;---------------------------------------------------------------------------- LCD_Initialize: movlw 15 call Wait_Wx1ms ; wait 15mS after power-up if LCD_lines==2 movlw 28h ; 4-bits interface, 2 lines, 5x7 dot font else movlw 20h ; 4-bits interface, 1 line, 5x7 dot font endif call LCD_SendCmd movlw 5 call Wait_Wx1ms ; wait 5mS if LCD_lines==2 movlw 28h ; 4-bits interface, 2 lines, 5x7 dot font else movlw 20h ; 4-bits interface, 1 line, 5x7 dot font endif call LCD_SendCmd movlw 10 ; wait 100uS call Wait_Wx10us movlw 06h ; entry mode: increment mode, no shift display call LCD_SendCmd movlw 0Eh ; Cursor ON, Display ON, Blinking OFF call LCD_SendCmd movlw 01h ; Clear display and cursor home goto LCD_SendCmd ;=========================================================================== ;=========================================================================== ;; c) Additional functions. Remove those not used by your application ;=========================================================================== ;=========================================================================== ;---------------------------------------------------------------------------- ; LCD_CleanUp ; Clears display and returns cursor to home position (address 00) ;---------------------------------------------------------------------------- LCD_CleanUp: movlw 0x01 ; command 01 call LCD_SendCmd movlw 2 ; wait 2 mS goto Wait_Wx1ms ;---------------------------------------------------------------------------- ; LCD_CursorLeft: ; Shift cursor one position to the left ;---------------------------------------------------------------------------- LCD_CursorLeft: movlw 0x10 goto LCD_SendCmd ;---------------------------------------------------------------------------- ; LCD_CursorRight: ; Shift cursor one position to the right ;---------------------------------------------------------------------------- LCD_CursorRight: movlw 0x14 goto LCD_SendCmd ;---------------------------------------------------------------------------- ; LCD_Home: ; Command 02H: Returns cursor to home position. Returns shifted display ; to original position. Does not clear display. ; LCD execution time: 40uS to 1.6mS ;---------------------------------------------------------------------------- LCD_Home: movlw 0x02 ; Command 02H call LCD_SendCmd movlw 2 ; wait 2 mS goto Wait_Wx1ms ;---------------------------------------------------------------------------- ; LCD_GetAddr (LGA) ; Current address is returned in "LCD_addr" ;---------------------------------------------------------------------------- LCD_GetAddr: call iLCD_WaitReady ; set all data lines as inputs bsf status,rp0 ; select bank 1 movlw ioMaskR ; mask to set LCD data lines as inputs movwf tris_LCD ; use mask in W to program port bcf status,rp0 ; select bank 0 ; read address, high nibble bcf port_RS,ioLCD_RS ; RS=0 signal it is a command bsf port_RW,ioLCD_RW ; R/W=1 signal it is a read operation nop ; wait 1us to comply with timming requirements bsf port_E,ioLCD_E ; E=1 enable LCD nop ; wait 1us to comply with timming requirements movf port_LCD,w ; read data lines movwf LCD_addr ; save bcf port_E,ioLCD_E ; E=0 disable LCD if (ioLCD_D7 != 7) ; if D7-D4 not conected to high nibble of PIC port swapf LCD_addr,f ; move data to high nibble endif movlw 0x0f0 andwf LCD_addr,f ; low nibble to ceros ; read the low order nibble bsf port_E,ioLCD_E ; E=1 enable LCD nop ; wait 1us to comply with timming requirements movf port_LCD,w ; read data lines movwf LCD_saveW ; save data in saveW bcf port_E,ioLCD_E ; E=0 disable LCD if (ioLCD_D7 == 7) ; if D7-D4 conected to high nibble of PIC port swapf LCD_saveW,f ; move data to low nibble endif movlw 0x0f andwf LCD_saveW,f ; high nibble to ceros movf LCD_saveW,w iorwf LCD_addr,f ; merge both nibbles ; reprogram all LCD data lines as outputs bsf status,rp0 ; select bank 1 movlw ioMaskW ; mask to set LCD data lines as outputs movwf tris_LCD ; program port bcf status,rp0 ; select bank 0 return ;---------------------------------------------------------------------------- ; LCD_WriteChar ; Writes char LCD_char at logical address LCD_addr. LCD_char is not changed ; ; The display internal RAM is 80 chars. If the display size is less than ; 80 chars what is on the screen is a "window" on the RAM. What is ; displayed depends on the entry mode settings. This RAM memory is ; divided into two lines: addresses 80h-A7h contains the information ; to display in the first LCD line, and addresses C0h-E7h contains ; the second line. ; ; When a 1x16 LCD type built with only one Hitachi controller is used, ; the first 8 displayed positions are mapped to addresses 80h-87h (first ; line memory) and the last half of the line is mapped to addresses ; C0h-C7h (second line memory). This complicates the application ; program as addressing is not linear. For example, you must split the ; messages to display. ; ; In order to avoid the complexities in your program, the routines ; LCD_putc and LCD_puts take care of all this address housekeeping. ;---------------------------------------------------------------------------- LCD_WriteChar: ; void LCD_WriteChar(char, LCD_addr) { bsf LCD_addr,7 ; set msb of LCD_adr if (LCD_lines == 1) movlw 0C0h ; if (LCD_addr >= C0h) subwf LCD_addr,w btfsc status,c goto LEC_addrOk ; goto address OK movlw 88h ; if (LCD_addr > 87h) subwf LCD_addr,w btfss status,c goto LEC_addrOk ; { movlw 38h ; NewAddr = 40h+LCD_addr-8 addwf LCD_addr,f ; } endif LEC_addrOk: movf LCD_addr,w ; MoveCursor(LCD_addr) call LCD_SetDataAddr movf LCD_char,w ; putc(char) goto LCD_SendData ; } ;---------------------------------------------------------------------------- ; LCD_putc ; Writes char W at current logical address. Address is incremented. ;---------------------------------------------------------------------------- LCD_putc: ; void LCD_putc(char c) ; { movwf LCD_char ; LCD_char = c call LCD_GetAddr ; LCD_addr = GetAddr() goto LCD_WriteChar ; WriteChar(LCD_char, LCD_addr) ; } ;---------------------------------------------------------------------------- ; LCD_EEputs (LEE) ; Writes ASCIIZ string from EEDATA memory at current LCD logical address. ; Address is incremented by size of string ;---------------------------------------------------------------------------- LCD_EEputs: ; void LCD_EEputs(char *s) ; { movwf eeadr ; ptr = s LEE_loop: ; while (*ptr != 0) bsf status,rp0 ; select bank 1 bsf eecon1,rd ; perform read: eedata= *eeadr bcf status,rp0 ; return to bank 0 movf eedata,w ; w = *ptr btfsc status,z ; if (w==0) return. End of string return call LCD_putc ; putc(w) incf eeadr,f ; ptr++ goto LEE_loop ; } ; } ;---------------------------------------------------------------------------- ; LCD_puts (LPS) ; Escritura l¢gica en el LCD del string "tira" en la posici¢n actual ; del cursor. ; No destruye ningun registro. ; ; dptr (*tira): ptr a tira a escribir en el LCD ;---------------------------------------------------------------------------- LCD_puts: ; void LCD_puts(char *tira) ifdef NO_VALE push dph ; { push dpl push acc ; char a LPS_Otro: ; while((a=*dptr) != '\0') movlw 0 movc a,@a+dptr jnz LPS_Enviar sjmp LPS_Fin LPS_Enviar: ; { call LCD_putc ; putc(a) inc dptr ; dptr++ sjmp LPS_Otro ; } LPS_Fin: ; } /* LCD_puts */ pop acc pop dpl pop dph ret endif ;---------------------------------------------------------------------------- ; LCD_putns ; Escritura l¢gica en el LCD, en la posici¢n actual del cursor, del string ; definido tras la direcci¢n de retorno: ej.: ; call LCD_putns ; db "Texto a escribir",0 ; ; DESTRUYE: A, DPTR ;---------------------------------------------------------------------------- LCD_putns: return ;**************************************************************************** ;**************************************************************************** ;** Timming routines start here ;**************************************************************************** ;**************************************************************************** ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; WNM- Wait_Wx1ms ; Execution remains in this routine just the milisecons specified in ; register W (1-255). If W==0 it is assumed 256ms. ; ; From a timming viewpoint, the sentence: ; call Wait_Wx1ms ; is executed in exactly W x 1ms (clock at 4MHz) ; Wait_Wx1ms: movwf nWaitTime ; save W. prolog 1: 1us WNM_Outer_loop: movlw 83 ; prolog 2: 2us movwf nWaitT2 ; n2 = 83 WNM_Middle_loop: ; prolog 3: 4us movlw 2 ; n3 = 2 movwf nWaitT3 goto WNM_Inner_loop ; to increment prolog 3 in 2us WNM_Inner_loop: decfsz nWaitT3,F goto WNM_Inner_loop ;End_inner: ; d3 = 3*n3+prolog3-1 = 3*n3+3 = 9us decfsz nWaitT2,F goto WNM_Middle_loop ;End_Middle: ; d2 = (3+d3)*n2+prolog2-1 = (3+d3)*n2+1 = decfsz nWaitTime,f ; = (3+9)*83+1 = 997us goto WNM_Outer_loop ;End_outer: ; d1 = (3+d2)*n1+prolog1-1 = (3+d2)*n1-2 return ; total = d1+2 = (3+d2)*n1 = (3+997)*n1 = 1000*n1 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; WNC- Wait_Wx100us ; Execution remains in this routine just the tenths of milisecons ; specified in register W (1-255). If W==0 it is assumed 25.6ms. ; ; From a timming viewpoint, the sentence: ; call Wait_Wx100us ; is executed in W x 100us + 1 us (clock at 4MHz) ; Wait_Wx100us: movwf nWaitTime ; save W WNC_Outer_loop: movlw 0x20 ; n2 = 32 movwf nWaitT2 WNC_Inner_loop: decfsz nWaitT2,f goto WNC_Inner_loop ;End_inner: ; t2 = 3*n2+1 = 3*32+1 = 97us decfsz nWaitTime,f goto WNC_Outer_loop ;End_outer: ; t1 = (3+t2)*N-1 = (3+97)*N-1 = 100*N - 1 return ; total = t1+2 = 100*N+1 us ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; WNX- Wait_Wx10us ; Execution remains in this routine just the hundredths of milisecons ; specified in register W (1-255). If W==0 it is assumed 256x10us = 2.56ms ; ; From a timming viewpoint, the sentence: ; call Wait_Wx10us ; is executed in W x 10us + 1 us (clock at 4MHz) ; Wait_Wx10us: movwf nWaitTime ; save W. prolog 1: 1us WNX_Outer_loop: movlw 0x02 ; n2 = 2 movwf nWaitT2 WNX_Inner_loop: decfsz nWaitT2,f goto WNX_Inner_loop ;End_inner: ; t2 = 3*n2+1 = 3*2+1 = 7us decfsz nWaitTime,f goto WNX_Outer_loop ;End_outer: ; t1 = (3+t2)*N-1 = (3+7)*N-1 = 10*N - 1 return ; total = t1+2 = 10*N+1 us END