Post by thread:why??

Hi folks; I am new to pics so please forgive me!! Can anyone tell me why my first program does not work? The processor is a 16c84. pc equ 0h fsr equ 2h porta equ 5h portb equ 6h trisa equ 85h trisb equ 86h status equ 3h rp0 equ 5h org 0 main: call init_portb ; Initialisation of port call led_output ; Output to leds goto main init_portb: clrf portb ;Initialise port by setting output latches bsf status, rp0 ;select bank one movlw 0x00 ;value used to init port movwf trisb ;set port b to all outputs return led_output: movlw 0xAA movwf portb return That's it ! All I want it to do is to switch on some led's but when it tries to output to the port, it seems to alter the trisb!! Please help

Clewer,Brian <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> wrote: > Can anyone tell me why my first program does not work? > The processor is a 16c84. > > .... > > init_portb: > clrf portb > bsf status, rp0 > movlw 0x00 > movwf trisb > return Brian: You need a "BCF STATUS, RP0" after the "MOVWF TRISB". Everything will work fine after you add it. -Andy Andrew Warren - fastfwdKILLspamix.netcom.com Fast Forward Engineering, Vista, California http://www.geocities.com/SiliconValley/2499

Brian, When you changed your access to Bank 1 to change the TRISB register, you didn't change back to Bank 0. See the code below, I've added the missing line. What are you using to develop the code? I highly recommend using MPLAB, or at least MPASM and MPSIM. I *never* burn a PIC (even 16C84) without simulating it six ways to Sunday (too much chance of a problem). Download MPSIM and it's manuals, print the manuals out and give it a shot. If you don't simulate, you'll just end up with a PIC that's sitting there and you don't know what's going on. myke {Quote hidden}>Hi folks; > I am new to pics so please forgive me!! >Can anyone tell me why my first program does not work? >The processor is a 16c84. > >pc equ 0h >fsr equ 2h >porta equ 5h >portb equ 6h >trisa equ 85h >trisb equ 86h >status equ 3h >rp0 equ 5h > > >org 0 > >main: > call init_portb ; Initialisation of port > call led_output ; Output to leds > goto main > > >init_portb: > clrf portb ;Initialise port by setting output latches > bsf status, rp0 ;select bank one > movlw 0x00 ;value used to init port > movwf trisb ;set port b to all outputs bcf status, rp0 ; Return to Bank 0 for Access >return ; Will the "return" line on the first column be ; seen as a label? {Quote hidden}> > > >led_output: > movlw 0xAA > movwf portb >return > > > > > >That's it ! > >All I want it to do is to switch on some led's but when it tries to output >to the port, it seems to alter the trisb!! > >Please help > > Avoiding precedents does not mean nothing should ever be done. It only means that nothing should ever be done for the first time - Sir Humphrey Appleby K.C.B.

> > Hi folks; > I am new to pics so please forgive me!! > Can anyone tell me why my first program does not work? Because port TRISB is in the upper register bank and you never set it back to bank 0 after setting trisb. Thee options: 1) Set the bank register bit to 1 (this is bit 5 of the status register RP0) You did this. but you didn't set it back to zero afterwards... 2) Put the address of the TRIS register into FSR and access via indirect. 3) Use the TRIS instruction. In fact this very reason was the sole purpose of the TRIS instruction, so you don't have to bank switch to do the tris stuff. BAJ {Quote hidden}> The processor is a 16c84. > > pc equ 0h > fsr equ 2h > porta equ 5h > portb equ 6h > trisa equ 85h > trisb equ 86h > status equ 3h > rp0 equ 5h > > > org 0 > > main: > call init_portb ; Initialisation of port > call led_output ; Output to leds > goto main > > > init_portb: > clrf portb ;Initialise port by setting output latches > bsf status, rp0 ;select bank one > movlw 0x00 ;value used to init port > movwf trisb ;set port b to all outputs > return > > > > led_output: > movlw 0xAA > movwf portb > return > > > > > > That's it ! > > All I want it to do is to switch on some led's but when it tries to output > to the port, it seems to alter the trisb!! > > Please help >

Clewer,Brian wrote: {Quote hidden}> > Hi folks; > I am new to pics so please forgive me!! > Can anyone tell me why my first program does not work? > The processor is a 16c84. > > pc equ 0h > fsr equ 2h > porta equ 5h > portb equ 6h > trisa equ 85h > trisb equ 86h > status equ 3h > rp0 equ 5h > > org 0 > > main: > call init_portb ; Initialisation of port > call led_output ; Output to leds > goto main > > init_portb: > clrf portb ;Initialise port by setting output latches > bsf status, rp0 ;select bank one > movlw 0x00 ;value used to init port > movwf trisb ;set port b to all outputs > bcf status, rp0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |||||||||||||||||||||||||||||||||||||||||||||||||||| {Quote hidden}> return > > led_output: > movlw 0xAA > movwf portb > return > > That's it ! > > All I want it to do is to switch on some led's but when it tries to output > to the port, it seems to alter the trisb!! > > Please help You didn't return to PAGE 0 after setting up the direction. Look in the init_portb: routine -- Friendly Regards Tjaart van der Walt ______________________________________________________________ | Another sun-deprived R&D Engineer slaving away in a dungeon | |WASP International GSM vehicle tracking and datacomm solutions| | +27-(0)11-622-8686 | http://wasp.co.za | |______________________________________________________________|