> PICers,
>
> Sorry to rehash an old topic but I CAN'T get this HD44780 LCD
> programme to work with a 16F84. Tried everything.  What drives me nuts
> is that the
> same programme in a 16C57 works fine. Well, damn - what's going on?
> Anybody got ideas??
>
> Any help/advice/insights MUCH appreciated!
>
> Thanx - Ian
>
>  title lcdtst01
> ;
> ;CCT CONFIGURATION :
>                              ------   ------
> ; DAT_C, 74C922 =>       RA2 |1    ---   18| RA1         <= DAT_B,
> 74C922
> ; DAT_D, 74C922 =>       RA3 |2          17| RA0         <= DAT_A,
> 74C922
> ;     BATT TEST => T0CKI/RA4 |3          16| OSC1/CLKIN  <= 2MHz XTAL
> ;        +5 VDC ->     /MCLR |4          15| OSC2/CLKOUT <= 2MHz XTAL
> ;           GND ->       Vss |5   16F84  14| Vdd         <- +5 VDC
> ;    74C922, DA  <-  INT/RB0 |6          13| RB7        ->  LCD EN
> ;            NC  <-      RB1 |7          12| RB6        ->  LCD DT
> ;            NC  <-      RB2 |8          11| RB5        ->  LCD CK
> ;            NC  <-      RB3 |9          10| RB4        ->  NC
> ;                            ---------------
>
>  LIST p=16F84, F=INHX8M, R=HEX
>       errorlevel 0, -302, -305
>             ;302="register in operand not in "
>             ;305="Using Default Destination"
>
>  __CONFIG _CP_OFF & _WDT_OFF & _XT_OSC
>
>  include "p16f84.inc"
>  include "asc2lcd.inc"    ;The LCD alpha-numeric assignments
>
> ;*********************************************************
> ;VECTOR ASSIGNMENTS
> ;*********************************************************
> pic84    equ   0x01FD      ;MAX memory address
>
> ;*********************************************************
> ;LCD pin assignments
> ;*********************************************************
> EN       equ 7
> CH       equ 6
> CK       equ 5
>
> RS       equ 3       ;Bit #4 in LCDFLAGS determines Command\Character
> for
>                      ;the LCD
> ;*********************************************************
> ;FLAG REGISTER assignments
> ;*********************************************************
> VT        equ  2      ;VALID TRANSMISSION from 74C922 to RB0
>
> ;*********************************************************
> ;MACROS
> ;*********************************************************
> BANK_0 MACRO
>  bcf  STATUS,RP0       ;RP0=STATUS.b5
>  bcf  STATUS,RP1       ;RP1=STATUS.b6
>  ENDM
>
> BANK_1 MACRO
>  bsf STATUS,RP0
>  bcf STATUS,RP1
>  ENDM
>
> ;*********************************************************
> ;REGISTER ASSIGNMENTS
> ;BANK #0
> ;*********************************************************
>  CBLOCK 0x00C
> w_                     ;Stores w during interrupts
> STATUS_                ;A 'dummy' STATUS register
> PCLATH_
> FSR_
> flags                  ;A 'decision' register
> Keydata                ;Holds DATA NIBBLE from the 74C922
> count_00
> count_01
> count_02
> count_03
>
> ;LCD registers.
> temp                   ;Holds HEX data prior to conversion to ASCII
> w2                     ;Dummy w register used by nib_tx
> charac                 ;Data for the LCD
> LCDflag                ;Flags R/W, cursor status etc
> d10000                 ;ASCII digits
> d1000
> d100
> d10
> d01
> count
> count_10               ;PAGE #1 count registers, available for
> count_11               ;up to 3-loop counters
> count_12
> count_13
>  ENDC
>
> ;********************************************************
> ;Begin the MAIN PROGRAMME
> ;********************************************************
>  ;PAGE
>          org       0x00
> start    goto      main
>
>          org       0x04
> int      movwf     w_             ;Start interrupt routine
>          movf      STATUS,0

>          movwf     PCLATH_
>          movf      FSR,0
>          movwf     FSR_
> b1       nop                      ;Do nothing for now
>          nop
>
> int_ret  movlw     b'00011000'    ;Reset the INTCON bits BUT ...
>          movwf     INTCON         ;.. let the PIC set GIE upon retfie
>          movf      FSR,0
>          movwf     FSR
>          movf      PCLATH_
>          movwf     PCLATH
>          movf      STATUS_,0      ;Return from interrupt
>          swapf     w_             ;Flip & laod the w register
>          swapf     w_,w           ;without affecting the STATUS reg.
>          retfie

>
> ;*************************************************************
> ;Initialise the PIC84's PORTS.
> ;
> ;PIN ASSIGNMENTS
> ;RB0  ..  INPUT. Reads DR  (Active High) from 74C922
> ;RB1  ..  NC
> ;RB2  ..  NC
> ;RB3  ..  NC
> ;RB4  ..  NC
> ;RB5  ..  OUTPT to 74164 (CK)
> ;RB6  ..  OUTPT to 74164 (Data B = CH)
> ;RB7  ..  OUTPT to LCD (EN)
> ;
> ;RA0  ..  INPUT. Reads DAT_A from 74C922
> ;RA1  ..  INPUT. Reads DAT_B from 74C922
> ;RA2  ..  INPUT. Reads DAT_C from 74C922
> ;RA3  ..  INPUT. Reads DAT_D from 74C922
> ;RA4  ..  INPUT. NC.
> ;
> ;*************************************************************
> init     clrf    PORTB
>          BANK_1
>          movlw   b'00000001'    ;All except RB0 to be OUTPTs
>          movwf   TRISB
>          BANK_0
>          movlw   0x0F1          ; Make sure OUTPTs are OFF

>          retlw   0x00
>
> ;*********************************************************
> ;LCD ROUTINES
> ;
> ; LCDtx4  .. a routine to drive the HC44780 LCD in 4-bit
> ;            mode via a 3-wire interface.
> ;
> ; Data byte must already be in the CHARAC when the
> ; routine is called. Data format ... D7 D6 D5 D4 RS x x x
> ;This routine shifts a NIBBLE of Data into the LCD but does so
> ;using a BYTE count. Data must be in the HIGH NIBBLE of the
> ;charac register.
> ;************************************************************
> lcdtx4   movlw    0x08
>          IFDEF DEBUG
>            goto lcdout
>          ENDIF
>
>          movwf    count
>          bcf      STATUS,C
>          bcf      PORTB,CK
>          nop                    ;Rest between bit ops.
>          bsf      PORTB,CH      ;Initialise the Data port.
> rotate   rlf      charac,1      ;Rotate the the Data thru CARRY, MSB
> first.
>          btfss    STATUS,C      ;Data bit = 1?
>           bcf     PORTB,CH      ;No  - send a zero
>          nop                    ;Rest between bit ops.
>          bsf      PORTB,CK      ;Clock the bit thru
>          nop
>          nop                    ;Rest between bit ops.
>          bcf      PORTB,CK
>          decfsz   count,1       ;Stepped down thru 8 bits?
>           goto    rotate-1      ;No  - keep clockin'
>          nop                    ;Rest between bit-ops.
>          bsf      PORTB,EN      ;Enable the LCD and
>          nop
>          nop
>          nop
>          nop                    ;transfer the Data.
>          bcf      PORTB,EN
>          nop
> lcdout   bcf      PORTB,CH      ;Leave PORTB in a defined state. All
> LOW.
>          retlw    0x00          ;Return to calling routine in PAGE #1
>
> ;**************************************************************
> ;NIB_TX takes a Data byte and puts the LS nibble into the HIGH
> ;nibble of the charac register. Data byte must be in the w register.
> ;NIB_TX checks RS of the LCDflags register to determine CHARACTER or
> ;COMMAND mode for the LCD
> ;*****************************************************************
> nib_tx  movwf    w2           ;w2 a VIRTUAL w register.. NOT w_
>         movlw    b'11110000'  ;Isolate the upper nibble and
>         andwf    w2,0         ;retrieve it in w.
>         movwf    charac       ;Stash the processed byte in charac
>         btfsc    LCDflag,RS   ;RS=0? COMMAND mode?
>          bsf     charac,3     ;No - set RS line for CHARACTER mode.
>         call     lcdtx4       ;and send it to the LCD.
>         IFNDEF DEBUG
>          call     DLY160      ;Wait 160 us till the LCD settles
>         ENDIF
>         swapf    w2,1         ;Invert the H & L nibbles
>         movlw    b'11110000'
>         andwf    w2,0         ;Isolate the new upper 4 digits
>         movwf    charac       ;and store in charac register.
>         btfsc    LCDflag,RS   ;RS=0? COMMAND mode?
>          bsf     charac,3     ;No  - set RS line for CHARACTER mode.
>         call     lcdtx4       ;Send'em to the LCD
>         IFNDEF DEBUG
>          call     DLY160      ;Wait 160 uS till the LCD settles.
>         ENDIF
>         retlw    0x00         ;Go back to page #1 calling routine
>
> ;****************************************************************
> ;DLY160 ... a one-loop, 160 usec (2.0MHz xtal) delay routine
> ;Both LCD delay routines are called from PAGE #1 and return there.
> ;DRTE : July 14, 1999
> ;*****************************************************************
> DLY160   movlw    0x05F        ;0x050 Calculate C1= 4F (d79) for T=160
> us)
>          movwf    count_11
>          decfsz   count_11,1
>           goto    $-1
>          retlw    0x00
>
> ;****************************************************************
> ;DLY_5 ...  A two-loop, 5-m sec (2.0 MHz xtal) delay routine.
> ;Both LCD delay routines are called from PAGE #1 and return there.
> ;DRTE  : July 14, 1999
> ;****************************************************************
> DLY_5    movlw    0x01F      ;0x0F calculate C2=$0A (d10) for T = 5
> msec
>          movwf    count_12
>          movlw    0x0FF
>          movwf    count_11
>          decfsz   count_11,1
>           goto    $-1
>          decfsz   count_12,1
>           goto    $-5
>          retlw    0x00
>
> ;**********************************************************
> ;Main Programme  .. begin from upper half of Bank #0. Turn
> ;the interrupts OFF till we're configured.
> ;**********************************************************
> main    ;bcf      INTCON,GIE   ;Switch off interrupts while we  ...
>         BANK_0
>         call     init         ;Initialise the ports
>
> ;***********************************************************
> ;Power up and configure the LCD
> ;***********************************************************
> pwr_up   clrf     LCDflag
>          bcf      LCDflag,RS  ;Clear RS.. COMMAND mode ENABLED
>          IFNDEF DEBUG
>           call    DLY_5       ;Wait 15 ms after switch-on
>           call    DLY_5
>           call    DLY_5
>           call    DLY_5
>          ENDIF
>
>          movlw    b'00110000' ;Write 0x03 to the LCD three
>          movwf    charac      ;times with suitable delays
>          call     lcdtx4      ;RS=0 for COMMAND instructions
>          IFNDEF DEBUG
>           call    DLY_5
>          ENDIF
>
>          movlw    b'00110000'
>          movwf    charac
>          call     lcdtx4
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
>          movlw    b'00110000'
>          movwf    charac
>          call     lcdtx4
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
>          movlw    b'00100000'  ;4 bit interface
>          movwf    charac
>          call     lcdtx4
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
> ;***************************************************************
> ;The following instrucs require 2 only NIBBLE WRITES to the LCD.
> ;Pass the parameters to the NIB_TX subroutine in w. NIB_TX will
> ;call the lcd_tx4 subroutine. BEWARE the nest level!!
> ;***************************************************************
>          movlw    b'00101000'    ;Write FUNCTION SET
>          call     nib_tx
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
>          movlw    b'00001110'    ;Write ON/OFF
>          call     nib_tx
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
>          movlw    b'00000110'   ;write ENT MODE
>          call     nib_tx
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
>          movlw    b'00000011'   ;Return Cursor & LCD to home
>          call     nib_tx
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
> ;************************************************************
> ;Then display a "WAKE UP" message ...
> ;************************************************************
> wakeup   movwf    charac
>          IFNDEF DEBUG
>           call    DLY_5
>          ENDIF
>
>          clrf     LCDflag
>          bsf      LCDflag,RS    ;Set RS=1 for CHARACTER mode.
>                                 ;Enable the 4 bit operating mode.
>          movlw    lcd_I         ;Load 'I' =  B'01001001'
>          call     nib_tx
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
>          movlw    lcd_A         ;Load 'A' = B'01000001'
>          call     nib_tx
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
>          movlw    lcd_N         ;Load 'N' = B'01001110'
>          call     nib_tx
>          IFNDEF DEBUG
>           call    DLY160
>          ENDIF
>
> setint  nop                        ;Forget interrupts till the LCD
> works!
>         ;BANK_1
>         ;movlw    0x0D
>         ;movwf    OPTION_REG
>         ;BANK_0
>         ;clrf     TMR0
>         ;movlw    b'10011000'      ;Enable the interrupts
>         ;movwf    INTCON
>         ;clrf     flags            ;Initialise the flags
>
>         goto    wakeup             ;Hold it here
>         end
>
> --
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>
>
>
>

>
> On Mon, 5 Feb 2001, Ian Hynes wrote:
>
> > PICers,
> >
> > Sorry to rehash an old topic but I CAN'T get this HD44780 LCD
> > programme to work with a 16F84. Tried everything.  What drives me nuts
> > is that the
> > same programme in a 16C57 works fine. Well, damn - what's going on?
> > Anybody got ideas??
> >
> > Any help/advice/insights MUCH appreciated!
> >
> > Thanx - Ian
> >
> >  title lcdtst01
> > ;
> > ;CCT CONFIGURATION :
> >                              ------   ------
> > ; DAT_C, 74C922 =>       RA2 |1    ---   18| RA1         <= DAT_B,
> > 74C922
> > ; DAT_D, 74C922 =>       RA3 |2          17| RA0         <= DAT_A,
> > 74C922
> > ;     BATT TEST => T0CKI/RA4 |3          16| OSC1/CLKIN  <= 2MHz XTAL
> > ;        +5 VDC ->     /MCLR |4          15| OSC2/CLKOUT <= 2MHz XTAL
> > ;           GND ->       Vss |5   16F84  14| Vdd         <- +5 VDC
> > ;    74C922, DA  <-  INT/RB0 |6          13| RB7        ->  LCD EN
> > ;            NC  <-      RB1 |7          12| RB6        ->  LCD DT
> > ;            NC  <-      RB2 |8          11| RB5        ->  LCD CK
> > ;            NC  <-      RB3 |9          10| RB4        ->  NC
> > ;                            ---------------
> >
> >  LIST p=16F84, F=INHX8M, R=HEX
> >       errorlevel 0, -302, -305
> >             ;302="register in operand not in "
> >             ;305="Using Default Destination"
> >
> >  __CONFIG _CP_OFF & _WDT_OFF & _XT_OSC
> >
> >  include "p16f84.inc"
> >  include "asc2lcd.inc"    ;The LCD alpha-numeric assignments
> >
> > ;*********************************************************
> > ;VECTOR ASSIGNMENTS
> > ;*********************************************************
> > pic84    equ   0x01FD      ;MAX memory address
> >
> > ;*********************************************************
> > ;LCD pin assignments
> > ;*********************************************************
> > EN       equ 7
> > CH       equ 6
> > CK       equ 5
> >
> > RS       equ 3       ;Bit #4 in LCDFLAGS determines Command\Character
> > for
> >                      ;the LCD
> > ;*********************************************************
> > ;FLAG REGISTER assignments
> > ;*********************************************************
> > VT        equ  2      ;VALID TRANSMISSION from 74C922 to RB0
> >
> > ;*********************************************************
> > ;MACROS
> > ;*********************************************************
> > BANK_0 MACRO
> >  bcf  STATUS,RP0       ;RP0=STATUS.b5
> >  bcf  STATUS,RP1       ;RP1=STATUS.b6
> >  ENDM
> >
> > BANK_1 MACRO
> >  bsf STATUS,RP0
> >  bcf STATUS,RP1
> >  ENDM
> >
> > ;*********************************************************
> > ;REGISTER ASSIGNMENTS
> > ;BANK #0
> > ;*********************************************************
> >  CBLOCK 0x00C
> > w_                     ;Stores w during interrupts
> > STATUS_                ;A 'dummy' STATUS register
> > PCLATH_
> > FSR_
> > flags                  ;A 'decision' register
> > Keydata                ;Holds DATA NIBBLE from the 74C922
> > count_00
> > count_01
> > count_02
> > count_03
> >
> > ;LCD registers.
> > temp                   ;Holds HEX data prior to conversion to ASCII
> > w2                     ;Dummy w register used by nib_tx
> > charac                 ;Data for the LCD
> > LCDflag                ;Flags R/W, cursor status etc
> > d10000                 ;ASCII digits
> > d1000
> > d100
> > d10
> > d01
> > count
> > count_10               ;PAGE #1 count registers, available for
> > count_11               ;up to 3-loop counters
> > count_12
> > count_13
> >  ENDC
> >
> > ;********************************************************
> > ;Begin the MAIN PROGRAMME
> > ;********************************************************
> >  ;PAGE
> >          org       0x00
> > start    goto      main
> >
> >          org       0x04
> > int      movwf     w_             ;Start interrupt routine
> >          movf      STATUS,0
> *** Statement below is bad as itself changes the status register

>
> >
> > ;*************************************************************
> > ;Initialise the PIC84's PORTS.
> > ;
> > ;PIN ASSIGNMENTS
> > ;RB0  ..  INPUT. Reads DR  (Active High) from 74C922
> > ;RB1  ..  NC
> > ;RB2  ..  NC
> > ;RB3  ..  NC
> > ;RB4  ..  NC
> > ;RB5  ..  OUTPT to 74164 (CK)
> > ;RB6  ..  OUTPT to 74164 (Data B = CH)
> > ;RB7  ..  OUTPT to LCD (EN)
> > ;
> > ;RA0  ..  INPUT. Reads DAT_A from 74C922
> > ;RA1  ..  INPUT. Reads DAT_B from 74C922
> > ;RA2  ..  INPUT. Reads DAT_C from 74C922
> > ;RA3  ..  INPUT. Reads DAT_D from 74C922
> > ;RA4  ..  INPUT. NC.
> > ;
> > ;*************************************************************
> > init     clrf    PORTB
> >          BANK_1
> >          movlw   b'00000001'    ;All except RB0 to be OUTPTs
> >          movwf   TRISB
> >          BANK_0
> >          movlw   0x0F1          ; Make sure OUTPTs are OFF
> *** RB2..4 will be low, RB4..7 will be high...

> >          movwf   PORTB
> >
> >          clrf    PORTA
> >          BANK_1
> >          movlw   0x01F
> >          movwf   TRISA
> >          BANK_0
> >          movlw   0x01F          ;PORTA to be all INPUTs
> >          movwf   PORTA          ;Bits 0,1,2,3,4 set to "1"
> *** to write to inputs does not make any sense

> >          retlw   0x00
> >
> > ;*********************************************************
> > ;LCD ROUTINES
> > ;
> > ; LCDtx4  .. a routine to drive the HC44780 LCD in 4-bit
> > ;            mode via a 3-wire interface.
> > ;
> > ; Data byte must already be in the CHARAC when the
> > ; routine is called. Data format ... D7 D6 D5 D4 RS x x x
> > ;This routine shifts a NIBBLE of Data into the LCD but does so
> > ;using a BYTE count. Data must be in the HIGH NIBBLE of the
> > ;charac register.
> > ;************************************************************
> > lcdtx4   movlw    0x08
> >          IFDEF DEBUG
> >            goto lcdout
> >          ENDIF
> >
> >          movwf    count
> >          bcf      STATUS,C
> >          bcf      PORTB,CK
> >          nop                    ;Rest between bit ops.
> >          bsf      PORTB,CH      ;Initialise the Data port.
> > rotate   rlf      charac,1      ;Rotate the the Data thru CARRY, MSB
> > first.
> >          btfss    STATUS,C      ;Data bit = 1?
> >           bcf     PORTB,CH      ;No  - send a zero
> >          nop                    ;Rest between bit ops.
> >          bsf      PORTB,CK      ;Clock the bit thru
> >          nop
> >          nop                    ;Rest between bit ops.
> >          bcf      PORTB,CK
> >          decfsz   count,1       ;Stepped down thru 8 bits?
> >           goto    rotate-1      ;No  - keep clockin'
> >          nop                    ;Rest between bit-ops.
> >          bsf      PORTB,EN      ;Enable the LCD and
> >          nop
> >          nop
> >          nop
> >          nop                    ;transfer the Data.
> >          bcf      PORTB,EN
> >          nop
> > lcdout   bcf      PORTB,CH      ;Leave PORTB in a defined state. All
> > LOW.
> >          retlw    0x00          ;Return to calling routine in PAGE #1
> >
> > ;**************************************************************
> > ;NIB_TX takes a Data byte and puts the LS nibble into the HIGH
> > ;nibble of the charac register. Data byte must be in the w register.
> > ;NIB_TX checks RS of the LCDflags register to determine CHARACTER or
> > ;COMMAND mode for the LCD
> > ;*****************************************************************
> > nib_tx  movwf    w2           ;w2 a VIRTUAL w register.. NOT w_
> >         movlw    b'11110000'  ;Isolate the upper nibble and
> >         andwf    w2,0         ;retrieve it in w.
> >         movwf    charac       ;Stash the processed byte in charac
> >         btfsc    LCDflag,RS   ;RS=0? COMMAND mode?
> >          bsf     charac,3     ;No - set RS line for CHARACTER mode.
> >         call     lcdtx4       ;and send it to the LCD.
> >         IFNDEF DEBUG
> >          call     DLY160      ;Wait 160 us till the LCD settles
> >         ENDIF
> >         swapf    w2,1         ;Invert the H & L nibbles
> >         movlw    b'11110000'
> >         andwf    w2,0         ;Isolate the new upper 4 digits
> >         movwf    charac       ;and store in charac register.
> >         btfsc    LCDflag,RS   ;RS=0? COMMAND mode?
> >          bsf     charac,3     ;No  - set RS line for CHARACTER mode.
> >         call     lcdtx4       ;Send'em to the LCD
> >         IFNDEF DEBUG
> >          call     DLY160      ;Wait 160 uS till the LCD settles.
> >         ENDIF
> >         retlw    0x00         ;Go back to page #1 calling routine
> >
> > ;****************************************************************
> > ;DLY160 ... a one-loop, 160 usec (2.0MHz xtal) delay routine
> > ;Both LCD delay routines are called from PAGE #1 and return there.
> > ;DRTE : July 14, 1999
> > ;*****************************************************************
> > DLY160   movlw    0x05F        ;0x050 Calculate C1= 4F (d79) for T=160
> > us)
> >          movwf    count_11
> >          decfsz   count_11,1
> >           goto    $-1
> >          retlw    0x00
> >
> > ;****************************************************************
> > ;DLY_5 ...  A two-loop, 5-m sec (2.0 MHz xtal) delay routine.
> > ;Both LCD delay routines are called from PAGE #1 and return there.
> > ;DRTE  : July 14, 1999
> > ;****************************************************************
> > DLY_5    movlw    0x01F      ;0x0F calculate C2=$0A (d10) for T = 5
> > msec
> >          movwf    count_12
> >          movlw    0x0FF
> >          movwf    count_11
> >          decfsz   count_11,1
> >           goto    $-1
> >          decfsz   count_12,1
> >           goto    $-5
> >          retlw    0x00
> >
> > ;**********************************************************
> > ;Main Programme  .. begin from upper half of Bank #0. Turn
> > ;the interrupts OFF till we're configured.
> > ;**********************************************************
> > main    ;bcf      INTCON,GIE   ;Switch off interrupts while we  ...
> >         BANK_0
> >         call     init         ;Initialise the ports
> >
> > ;***********************************************************
> > ;Power up and configure the LCD
> > ;***********************************************************
> > pwr_up   clrf     LCDflag
> >          bcf      LCDflag,RS  ;Clear RS.. COMMAND mode ENABLED
> >          IFNDEF DEBUG
> >           call    DLY_5       ;Wait 15 ms after switch-on
> >           call    DLY_5
> >           call    DLY_5
> >           call    DLY_5
> >          ENDIF
> >
> >          movlw    b'00110000' ;Write 0x03 to the LCD three
> >          movwf    charac      ;times with suitable delays
> >          call     lcdtx4      ;RS=0 for COMMAND instructions
> >          IFNDEF DEBUG
> >           call    DLY_5
> >          ENDIF
> >
> >          movlw    b'00110000'
> >          movwf    charac
> >          call     lcdtx4
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> >          movlw    b'00110000'
> >          movwf    charac
> >          call     lcdtx4
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> >          movlw    b'00100000'  ;4 bit interface
> >          movwf    charac
> >          call     lcdtx4
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> > ;***************************************************************
> > ;The following instrucs require 2 only NIBBLE WRITES to the LCD.
> > ;Pass the parameters to the NIB_TX subroutine in w. NIB_TX will
> > ;call the lcd_tx4 subroutine. BEWARE the nest level!!
> > ;***************************************************************
> >          movlw    b'00101000'    ;Write FUNCTION SET
> >          call     nib_tx
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> >          movlw    b'00001110'    ;Write ON/OFF
> >          call     nib_tx
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> >          movlw    b'00000110'   ;write ENT MODE
> >          call     nib_tx
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> >          movlw    b'00000011'   ;Return Cursor & LCD to home
> >          call     nib_tx
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> > ;************************************************************
> > ;Then display a "WAKE UP" message ...
> > ;************************************************************
> > wakeup   movwf    charac
> >          IFNDEF DEBUG
> >           call    DLY_5
> >          ENDIF
> >
> >          clrf     LCDflag
> >          bsf      LCDflag,RS    ;Set RS=1 for CHARACTER mode.
> >                                 ;Enable the 4 bit operating mode.
> >          movlw    lcd_I         ;Load 'I' =  B'01001001'
> >          call     nib_tx
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> >          movlw    lcd_A         ;Load 'A' = B'01000001'
> >          call     nib_tx
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> >          movlw    lcd_N         ;Load 'N' = B'01001110'
> >          call     nib_tx
> >          IFNDEF DEBUG
> >           call    DLY160
> >          ENDIF
> >
> > setint  nop                        ;Forget interrupts till the LCD
> > works!
> >         ;BANK_1
> >         ;movlw    0x0D
> >         ;movwf    OPTION_REG
> >         ;BANK_0
> >         ;clrf     TMR0
> >         ;movlw    b'10011000'      ;Enable the interrupts
> >         ;movwf    INTCON
> >         ;clrf     flags            ;Initialise the flags
> >
> >         goto    wakeup             ;Hold it here
> >         end
> >
> > --
> > http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> > email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body
> >
> >
> >
> >
> Sorry, I did not follow the whole part of code. However, as I recall,
> 74164 has a clear pin which should be considered.
>
> --
> http://www.piclist.com hint: To leave the PICList
> piclist-unsubscribe-requestspam_OUTmitvma.mit.edu
>
>

> Hey Bob & Imre,
>
> Thanks, I've been thru the corrections and made changes to the ISR.
> Imre's way of configuring the outpt is good - the LEDs go high right
> at the start ; can't see any low-going little glitches on a CRO.
>
> OK, the new init & ISR segments look like so :-
>
> init     movlw   b'11111111'
>          movwf   PORTB          ;Make PORTB all HIGH, avoid turn-on
> glitch??
>          BANK_1
>          movlw   b'00000001'    ;All except RB0 to be OUTPTs
>          movwf   TRISB
>          BANK_0
>          movlw   b'00011111'
>          movwf   PORTA
>          BANK_1
>          movlw   0x01F
>          movwf   TRISA
>          BANK_0
>          retlw   0x00
> ;<...................>
>         org       0x04
> int      movwf     w_             ;Start interrupt routine
>          movf      STATUS,0
>          movwf     STATUS_
>          movf      PCLATH,0       ;Save PCLATH
>          movwf     PCLATH_
>          movf      FSR,0
>          movwf     FSR_
> b1       nop            ;Do the interrupt routine
>                ;There are KPD & LED routines in here let's not confuse
> things ...
> b2       nop            ;Send the result to RS232
>
> int_ret  movlw     b'00011000'    ;Reset the INTCON bits BUT ...
>          movwf     INTCON         ;.. let the PIC set GIE upon retfie
>          movf      FSR,0

>          movwf     FSR
>          movf      PCLATH_
>          movwf     PCLATH
>          movf      STATUS_,0      ;Return from interrupt
>          movwf     STATUS
>          swapf     w_             ;Flip & laod the w register
>          swapf     w_,w           ;without affecting the STATUS reg.
>          retfie
>
> The ISR works OK, as shown above. The cct grabs a nibble from a KPD
> via a 74C922 and lights up 4 LEDs with it.
>
> ***The only thing that's NOT working is the LCD. ***
>
> I made sure MPLAB is set to 2MHz, same as the cct, as Dave vanH
> suggested. And i can change LCD, 74164 etc over into the 16C57 cct and
> they work so it's not that ...
>
> Wait'll i fiddle some more with it guys ... I'd better repost anyway
> cuz I didn't put in the [PIC]: prefix originally. NEWTON's LAW
> applies!<GR>
>
>
> Bob Ammerman wrote:
> >
> > ----- Original Message -----
> > From: dr. Imre Bartfai <spamBeGonerootspamBeGonePROF.PMMF.HU>
> > To: <TakeThisOuTPICLISTEraseMEspam_OUTMITVMA.MIT.EDU>
> > Sent: Monday, February 05, 2001 2:03 AM
> > Subject: Re: [PIC]: LCD Problems
> >
> > > Hi,
> > > without studying your code in-depth, I see some typical problem in

> > > ISR. Critical places are marked below. I hope this helps.
> > >
> > > Regards,
> > > Imre
> >
> > Yikes! At least some of your corrections are incorrect!
> >
> > I've marked my opinion with "!!!" below.
> >
> > Bob Ammerman
> > RAm Systems
> > (contract development of high performance, high function, low-level
> > software)
> >
> > >
> > > On Mon, 5 Feb 2001, Ian Hynes wrote:
> > >
> > > > PICers,
> > > >
> > > > Sorry to rehash an old topic but I CAN'T get this HD44780 LCD
> > > > programme to work with a 16F84. Tried everything.  What drives me

> > > > is that the
> > > > same programme in a 16C57 works fine. Well, damn - what's going on?
> > > > Anybody got ideas??
> > > >
> > > > Any help/advice/insights MUCH appreciated!
> > > >
> > > >
> > > >  LIST p=16F84, F=INHX8M, R=HEX
>
> > > >          org       0x00
> > > > start    goto      main
> > > >
> > > >          org       0x04
> > > > int      movwf     w_             ;Start interrupt routine
> > > >          movf      STATUS,0
> > > *** Statement below is bad as itself changes the status register
> >
> > !!! I assume you meant to say 'statement above', but the original
> > !!! value of STATUS will be properlyy copied to W
>
> Yeah, OK ... bcf is bad. Leave page settings to the MACROS alone.
>
> >
> > > >          bcf       STATUS,0       ;Put registers into known page
> > > >          movwf     STATUS_
> > > >          movf      PCLATH,0       ;Save PCLATH
> > > *** sorry - PCLATH can not be read as spec gives.
> >
> > !!! Why not??
>
> Yeah, why not??
> >
> > > *** it is better not to change pages and set up save registers for
> > > *** every bank at the same location.
> >
> > !!! In the F84 all GPR is mapped in both banks 0 and 1 anyway
>
> True, but maybe keepthings unambiguous and use MACROs to change pages
> within the main prog or ISR?
> >
> > >
> > > >          movwf     PCLATH_
> > > >          movf      FSR,0
> > > >          movwf     FSR_
> > > > b1       nop                      ;Do nothing for now
> > > >          nop
> > > >
> > > > int_ret  movlw     b'00011000'    ;Reset the INTCON bits BUT ...
> > > >          movwf     INTCON         ;.. let the PIC set GIE upon

> >
> > !!! Normally you'd test bits in INTCON,
> > !!! handle the interrupt and then clear them
>
> Don't understand what you're getting at here?
>
> >
> > > >          movf      FSR,0
> > > >          movwf     FSR
> > > >          movf      PCLATH_
> > > >          movwf     PCLATH
> > > >          movf      STATUS_,0      ;Return from interrupt
> >
> > !!! You are missing a MOVWF STATUS here
> > !!! to restore the status register
>
> I see it  .. Thnax!
> >
> > > >          swapf     w_             ;Flip & laod the w register
> > > >          swapf     w_,w           ;without affecting the STATUS reg.
> > > >          retfie
> > >
> > > *** if you do not use IT's, there is no point to write an ISR
> >
> > !!! This is certainly true!
>
> I think the above is Myk Predko's trick for retrieving w. And there is
> an ISR in there (not shown).
> >
>  ..SNIP ...
> > > > ;*************************************************************
> > > > init     clrf    PORTB
> > > >          BANK_1
> > > >          movlw   b'00000001'    ;All except RB0 to be OUTPTs
> > > >          movwf   TRISB
> > > >          BANK_0
> > > >          movlw   0x0F1          ; Make sure OUTPTs are OFF
> > > *** RB2..4 will be low, RB4..7 will be high...
> >
> > !!! Yep, after 'glitching' to all lows becuase of the
> > !!! clrf PORTB, above
>
> Hmm ...hadn't thoughta that. There is a turn on glitch all right. See
> the new init routine above.
> >
> > > >          movwf   PORTB
> > > >
> > > >          clrf    PORTA
> > > >          BANK_1
> > > >          movlw   0x01F
> > > >          movwf   TRISA
> > > >          BANK_0
> > > >          movlw   0x01F          ;PORTA to be all INPUTs
> > > >          movwf   PORTA          ;Bits 0,1,2,3,4 set to "1"
> > > *** to write to inputs does not make any sense
> >
> > !!! Yep, plus RA4 is defined as an  "INPUT NC (no connection)"
> > !!! This is a bad idea (floating input).
>
> Agreed. Scrub that idea. Put LEDs on the floaters - active low config.
>
> >
> > !!! I stopped looking at the code, here (Bob A)
> >
> > > >          retlw   0x00
>
> > > Sorry, I did not follow the whole part of code. However, as I recall,
> > > 74164 has a clear pin which should be considered.
>
> No worries - that's held HIGH all the time as the three PORTB pins a
> re dedicated to the LCD.
>
> Regards - Ian
>
> --
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>
>