RobertD
New Member
Why not use internal oscillator....? That way you don't have to bother with the external clock, and associated circuit.
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That should be fine as long as you connect to the correct pins on the oscillator. By ground, I'll assume you know that it connects to pin 5 of the PIC also. The 4th pin of the oscillator may be a tuning pin. It depends on the type of oscillator. If you have problems, post the part number of the oscillator. The datasheet is on the net somewhere for me to see.
That should be fine. I believe the code you have was written for a PIC with a 4Mhz oscillator.
Yes, that would be the simplest thing. But the 16F84A doesn't have that option. The 16F628A does and is a drop in replacement for the 16F84A with some minor code changes. There is so much code on the net for the classic F84 that noobs still get tricked into using it.RobertD said:
Even the 16F628A is getting a little long in the tooth.My mistake. I thought you said you had an oscillator. You have a crystal if it only has 2 pins. When combined with the internal circuitry of the PIC and some caps, you have a crystal oscillator. For a 4Mhz crystal you would connect it like this:
d1 equ 0x0D //Making d1 equal 13
d2 equ 0x0E //Making d2 equal 14
d3 equ 0x0F //Making d3 equal 15
d4 equ 0x10 //Making d4 equal 16
org 0X000 //Set the following code to start at Address 0
goto Init //Jump to the beginning of the code.
//Mainly done as an interrupt thing, but not *really*
//needed unless you use interrupts
org 0X004 //Setting the code to start at Address 4
retfie //If an interrupt flag is set, it automatically jumps to 4.
//Not really needed if you're careful and make sure you're
//not setting up any Interrupts.
Init
bsf STATUS,RP0 //Switch to bank 1
clrf TRISB //Set all PORTB pins to output
clrf TRISA //Set all PORTA pins to output
bcf STATUS,RP0 //Switch back to bank 0.
clrf PORTA //Make sure PORTA pins are pulled low.
clrf PORTB //And PORTB pins, too.
Main
bsf PORTB,0 //Pull PORTB's first pin (RB0) high.
call Del5M //Call the Del5M subroutine. Skip the rest of Main for
//now.
bcf PORTB,0 //Welcome back to Main. Assuming all the dX registers
//(d1, d2, d3, and d4) are zeroed out, pull RB0 low
//again.
call Del5M //And now we go back to set up all the values and
//do that decfsz nonsense again. This time when it's
goto Main //done, we go back to the beginning of Main and
//pull RB0 high again. And it just repeats that like
//indefinitely.
Del5M
movlw 0x54 //Move the decimal 84 into W
movwf d1 //Move W into address defined in the EQU directive.
movlw 0xA1 //Just more moving values
movwf d2 //into registers. Doot de doo.
movlw 0xFD //Yep, more of the same.
movwf d3 //Weather's pretty nice today.
movlw 0x02 //Maybe I should mow the lawn.
movwf d4 //Okay, this part is done now.
Delay_0
decfsz d1, f //Here we decrease the value in the given register
//(d1 in this case). the ",f" afterwards just tells it
//to store the result back in the register it changed.
//If the register, however, is zero, the instruction
//makes the PIC skip the next instruction
goto $+2 //This instruction just says to jump two instructions.
//The $ value just means "current address", so one
//could also say "goto $-3" to go back 3 addresses,
//if the code needed that.
decfsz d2, f //Same old decfsz. Kind of a weird program flow going
goto $+2 //on here, but whatever floats their boat.
decfsz d3, f //It's early, I should probably get some breakfast.
goto $+2 //I've got some strawberry poptarts, that might do.
decfsz d4, f //Okay, almost done with this part.
goto Delay_0 //If d4 isn't zero yet, you have to go back to the
//beginning of this block of code and keep decfsz-ing
//until everything is zero. Then we move onto the
//next part.
;5 cycles
goto $+1 //These are just junk instructions, used because they
goto $+1 //take up 2 cycles each,
nop //when NOP only takes up 1 cycle and also does
return //nothing. Our Return here just makes us jump back
//to the main block. Let's go, shall we? Go back up.
end movlw 0xA1 //Just more moving values
movwf d2 //into registers. Doot de doo.
movlw 0xFD //Yep, more of the same.
movwf d3 //Weather's pretty nice today.
movlw 0x02 //Maybe I should mow the lawn.
movwf d4 //Okay, this part is done now.If your oscillator has two pins then you don't have an oscillator, you have a crystal. This is good, you connect your crystal to pins 15 and 16 and connect two small (30pf) capacitor from pins 15 and 16 to ground.
Edit, kcriste beat me to it and he remembered the config setting which I forgot.
Mike.
bsf STATUS,RP0
clrf TRISB[COLOR="Blue"] & 0x7f[/COLOR]
clrf TRISA[COLOR="blue"] & 0x7f[/COLOR]
bcf STATUS,RP0org 0X000
goto Init
org 0X004
retfie
