Pic16f818

blueroomelectronics · Nov 11, 2008

They do make smaller SOIC PICs

ericgibbs · Nov 11, 2008

Is the 16F876 PIC an option.?

futz · Nov 11, 2008

uaefame said:
The PIC16F877 is so big that it doesn't easily fit or can't even fit to the breadboard.

Any ideas?

Buy a **broken link removed**. I routinely use **broken link removed** ones with 40-pin chips. The **broken link removed** ones are nice too. How small is yours?

uaefame · Nov 11, 2008

Is the 16F876 PIC an option.?

I am using PIC 16F877 Ya the programming of PIC 16F876 is similar thanks GOD

.

I mean the pins are so high i mean they doesn't really fit inside the breadboard. The breadboard size is well but I think i need a socket with it.

blueroomelectronics · Nov 11, 2008

Actually the 16F877 & 876 use the same die, PORTD & E are simply not connected.

uaefame · Nov 12, 2008

I decided to understand the codes

I have 3 questions. First question about STATUS register.

Code:

bsf	STATUS,RP0
		bcf	STATUS,RP1
		bsf	STATUS,IRP

Here we set bank 1 for direct addressing and IRP which is bit 7 of status to 1 which mean bank 2, 3 which is indirect addressing.

Q1> What is the different between direct and indirect addressing?

Code:

radix dec

Q2> what is the meaning of this?

Code:

		cblock	20h
OnTime:2
OffTime:2
		endc

I am using PIC16F877 FYI, and here we r setting OnTime and OffTime in the general purpose resistor then we are adding :2?

Can you explain this line too.

Thanks in advance

uaefame · Nov 12, 2008

I run the simulation for Pommie codes

Code:

 ;*******************************************************************
;                           16F877 PWM Program
;*******************************************************************

		include	"p16f877.inc"

		errorlevel	-302
		radix	dec

	__CONFIG _CP_OFF & _DEBUG_ON & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & _LVP_OFF & _CPD_OFF

		cblock	20h
OnTime:2
OffTime:2
		endc

		cblock	71h
int_work
int_status 
int_pclath
		endc

		org     0h
		nop
		goto    start
		nop
		nop

interupt	movwf	int_work
		swapf	STATUS,W
		movwf	int_status
		bcf	STATUS,RP0
		bcf	STATUS,RP1
		movfw	PCLATH
		movwf	int_pclath
		clrf	PCLATH

		btfsc	PORTB,0
		goto	TurnOff
; turn on the output and write the on time
		nop;		delay to make both path identical
		bsf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OnTime+1
		movwf	CCPR1H
		movfw	OnTime
		movwf	CCPR1L
		goto	DonePWM

TurnOff		bcf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OffTime+1
		movwf	CCPR1H
		movfw	OffTime
		movwf	CCPR1L
DonePWM
		bcf	PIR1,CCP1IF;	reset special event trigger interupt

		movfw	int_pclath
		movwf	PCLATH
		swapf	int_status,W
		movwf	STATUS
		swapf	int_work,F;	swap to file
		swapf	int_work,W;	swap to work
		retfie


start		bsf	STATUS,RP0
		bcf	STATUS,RP1
		bsf	STATUS,IRP;	all indirest access is to 100h - 1ffh
		 movlw	(0<<NOT_RBPU|0<<INTEDG|0<<T0CS|0<<T0SE|0<<PSA|B'000'<<PS0)
		movwf	OPTION_REG
		movlw	b'11111110'
		movwf	TRISB
		bcf	STATUS,RP0
		movlw	(b'01'<<T1CKPS0|0<<T1OSCEN|0<<NOT_T1SYNC|0<<TMR1CS|1<<TMR1ON)
		movwf	T1CON;		enable timer 1
		movlw	low(45000)
		movwf	CCPR1L
		movwf	OnTime
		movlw	high(45000)
		movwf	CCPR1H
		movwf	OnTime+1
		movlw	low(5000)
		movwf	OffTime
		movlw	high(5000)
		movwf	OffTime+1
		movlw	(0<<CCP1X|0<<CCP1Y|b'1011'<<CCP1M0);	enable special event trigger on CCP1
		movwf	CCP1CON;	
		bsf	STATUS,RP0
		bsf	PIE1,CCP1IE;	enable CCP1 interupt
		bcf	STATUS,RP0

		movlw	(1<<GIE|1<<PEIE|0<<T0IE|0<<INTE|0<<RBIE|0<<T0IF|0<<INTF|0<<RBIF)
		movwf	INTCON;		enable Peripheral interupts

Loop		
		goto	Loop


		END

Its only go around Start then Loop Loop Loop Loop ... forever whatabout the remaining codes when they are called or used? Any ideas?

Unused code in my view

Code:

nop
		nop

interupt	movwf	int_work
		swapf	STATUS,W
		movwf	int_status
		bcf	STATUS,RP0
		bcf	STATUS,RP1
		movfw	PCLATH
		movwf	int_pclath
		clrf	PCLATH

		btfsc	PORTB,0
		goto	TurnOff
; turn on the output and write the on time
		nop;		delay to make both path identical
		bsf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OnTime+1
		movwf	CCPR1H
		movfw	OnTime
		movwf	CCPR1L
		goto	DonePWM

TurnOff		bcf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OffTime+1
		movwf	CCPR1H
		movfw	OffTime
		movwf	CCPR1L
DonePWM
		bcf	PIR1,CCP1IF;	reset special event trigger interupt

		movfw	int_pclath
		movwf	PCLATH
		swapf	int_status,W
		movwf	STATUS
		swapf	int_work,F;	swap to file
		swapf	int_work,W;	swap to work
		retfie

futz · Nov 12, 2008

uaefame said:
First question about STATUS register.

Code:

bsf STATUS,RP0 bcf STATUS,RP1 bsf STATUS,IRP

Here we set bank 1 for direct addressing and IRP which is bit 7 of status to 1 which mean bank 2, 3 which is indirect addressing.

Q1> What is the different between direct and indirect addressing?

I understand indirect addressing, but I don't know what IRP is for. I never diddle those bits directly. I let the assembler do it for me by using the banksel directive. Like this:

Code:

	org	0x0000
init
	banksel	TRISB		;bank 1
	movlw	0x06		;configure all pins
	movwf	ADCON1		;as digital inputs
	clrf	TRISB
	banksel	PORTA	;bank 0
main	bsf	PORTB,0
	call	delayc
	call	delay
	goto	main

--------------------------------------

Code:
Code:

radix dec

Q2> what is the meaning of this?

The radix sets which numbering system you want to be default. With the above line you've set the radix to decimal. So any number you use with no prefix or suffix (0x or h) is automatically understood to be in decimal. If you don't put any radix definition line in your source the default (I believe) is hexadecimal. I could be wrong. Test it and you'll soon know for sure.

--------------------------------------

Code:
Code:

cblock 20h OnTime:2 OffTime:2 endc

I am using PIC16F877 FYI, and here we r setting OnTime and OffTime in the general purpose resistor then we are adding :2?

Can you explain this line too.

In the cblock you're allocating space in RAM for two variables, OnTime and OffTime. The :2 tells the assembler to reserve 2 bytes for each variable instead of the usual 1 byte.

uaefame · Nov 12, 2008

PIC 16F877 has two VDD and VSS.

Do I need to connect 5V and ground to each one? Or one is enough?

Thanks in advance

futz · Nov 12, 2008

uaefame said:
PIC 16F877 has two VDD and VSS.

Do I need to connect 5V and ground to each one? Or one is enough?

Microchip says to connect all VDD and VSS pins.

uaefame · Nov 13, 2008

Here are Pomie codes

Code:

  ;*******************************************************************
;                           16F877 PWM Program
;*******************************************************************

		include	"p16f877.inc"

		errorlevel	-302
		radix	dec

	__CONFIG _CP_OFF & _DEBUG_ON & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & _LVP_OFF & _CPD_OFF

		cblock	20h
OnTime:2
OffTime:2
		endc

		cblock	71h
int_work
int_status 
int_pclath
		endc

		org     0h
		nop
		goto    start
		nop
		nop

interupt	movwf	int_work
		swapf	STATUS,W
		movwf	int_status
		bcf	STATUS,RP0
		bcf	STATUS,RP1
		movfw	PCLATH
		movwf	int_pclath
		clrf	PCLATH

		btfsc	PORTB,0
		goto	TurnOff
; turn on the output and write the on time
		nop;		delay to make both path identical
		bsf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OnTime+1
		movwf	CCPR1H
		movfw	OnTime
		movwf	CCPR1L
		goto	DonePWM

TurnOff		bcf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OffTime+1
		movwf	CCPR1H
		movfw	OffTime
		movwf	CCPR1L
DonePWM
		bcf	PIR1,CCP1IF;	reset special event trigger interupt

		movfw	int_pclath
		movwf	PCLATH
		swapf	int_status,W
		movwf	STATUS
		swapf	int_work,F;	swap to file
		swapf	int_work,W;	swap to work
		retfie


start		bsf	STATUS,RP0
		bcf	STATUS,RP1
		bsf	STATUS,IRP;	all indirest access is to 100h - 1ffh
		 movlw	(0<<NOT_RBPU|0<<INTEDG|0<<T0CS|0<<T0SE|0<<PSA|B'000'<<PS0)
		movwf	OPTION_REG
		movlw	b'11111110'
		movwf	TRISB
		bcf	STATUS,RP0
		movlw	(b'01'<<T1CKPS0|0<<T1OSCEN|0<<NOT_T1SYNC|0<<TMR1CS|1<<TMR1ON)
		movwf	T1CON;		enable timer 1
		movlw	low(45000)
		movwf	CCPR1L
		movwf	OnTime
		movlw	high(45000)
		movwf	CCPR1H
		movwf	OnTime+1
		movlw	low(5000)
		movwf	OffTime
		movlw	high(5000)
		movwf	OffTime+1
		movlw	(0<<CCP1X|0<<CCP1Y|b'1011'<<CCP1M0);	enable special event trigger on CCP1
		movwf	CCP1CON;	
		bsf	STATUS,RP0
		bsf	PIE1,CCP1IE;	enable CCP1 interupt
		bcf	STATUS,RP0

		movlw	(1<<GIE|1<<PEIE|0<<T0IE|0<<INTE|0<<RBIE|0<<T0IF|0<<INTF|0<<RBIF)
		movwf	INTCON;		enable Peripheral interupts

Loop		
		goto	Loop


		END

I modified it and here is the new codes

Code:

;*******************************************************************
;                           16F877 PWM Program
;*******************************************************************

		include	"p16f877.inc"

		errorlevel	-302
		radix	dec

	__CONFIG _CP_OFF & _DEBUG_ON & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & _LVP_OFF & _CPD_OFF

		cblock	20h
OnTime:2
OffTime:2
		endc

		cblock	71h
int_work
int_status 
int_pclath
		endc

		org     0h
		nop
		goto    start
		nop
		nop
		org 	04h
		goto    interupt
interupt	movwf	int_work
		swapf	STATUS,W
		movwf	int_status
		bcf	STATUS,RP0
		bcf	STATUS,RP1
		movfw	PCLATH
		movwf	int_pclath
		clrf	PCLATH

		btfsc	PORTB,0
		goto	TurnOff
; turn on the output and write the on time
		nop;		delay to make both path identical
		bsf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OnTime+1
		movwf	CCPR1H
		movfw	OnTime
		movwf	CCPR1L
		goto	DonePWM

TurnOff		bcf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OffTime+1
		movwf	CCPR1H
		movfw	OffTime
		movwf	CCPR1L
DonePWM
		bcf	PIR1,CCP1IF;	reset special event trigger interupt

		movfw	int_pclath
		movwf	PCLATH
		swapf	int_status,W
		movwf	STATUS
		swapf	int_work,F;	swap to file
		swapf	int_work,W;	swap to work
		retfie


start		bsf	STATUS,RP0
		bcf	STATUS,RP1
		bsf	STATUS,IRP;	all indirest access is to 100h - 1ffh
		 movlw	(0<<NOT_RBPU|0<<INTEDG|0<<T0CS|0<<T0SE|0<<PSA|B'000'<<PS0)
		movwf	OPTION_REG
		movlw	b'11111110'
		movwf	TRISB
		bcf	STATUS,RP0
		movlw	(b'01'<<T1CKPS0|0<<T1OSCEN|0<<NOT_T1SYNC|0<<TMR1CS|1<<TMR1ON)
		movwf	T1CON;		enable timer 1
		movlw	low(45000)
		movwf	CCPR1L
		movwf	OnTime
		movlw	high(45000)
		movwf	CCPR1H
		movwf	OnTime+1
		movlw	low(5000)
		movwf	OffTime
		movlw	high(5000)
		movwf	OffTime+1
		movlw	(0<<CCP1X|0<<CCP1Y|b'1011'<<CCP1M0);	enable special event trigger on CCP1
		movwf	CCP1CON;	
		bsf	STATUS,RP0
		bsf	PIE1,CCP1IE;	enable CCP1 interupt
		bcf	STATUS,RP0

		movlw	(1<<GIE|1<<PEIE|0<<T0IE|0<<INTE|0<<RBIE|0<<T0IF|0<<INTF|0<<RBIF)
		movwf	INTCON;		enable Peripheral interupts

Loop		
		goto	Loop


		END

I only did this change

Code:

		org 	04h
		goto    interupt

My Main question how does the program call the interupt command? I mean the interupt loop?

I added these codes is it right or i need to remove it?

ericgibbs · Nov 13, 2008

hi,
The ISR [interrupt service routine] is called by the STATE of bits set by the PIC's internal peripherals or external interrupts.

EDIT your post by selecting ALL the code text and then click the '#' sign on the menu bar. This will keep the formatting for the code text.

I see you changed it while I was replying.

Pommie · Nov 13, 2008

The interrupt (I must learn how to spell interrupt) code is run when the CCP1 interrupt is triggered. To use the code you would set On_Time and Off_Time in the empty Loop (2500=1mS). Adding the goto is a bad thing and could cause the pic to crash if more code is added.

Mike.

uaefame · Nov 13, 2008

Interesting,

I somehow enjoy learning PIC I don't know why

. Maybe Because you guys keep helping me

To use the code you would set On_Time and Off_Time in the empty Loop (2500=1mS).

Can you explain it?

I am just interested in knowing how On_Time and Off_Time can actually call interrput? Is the formating an issue? Or There is a special way of triggering the interrput codes. Its amazing how interput will be excuted even though you didn't tell the program about it.
I mean like goto interrput and call interrput?

hi eric

STATE

you mean STATUS? or STATE because i can't find STATE in the register file map?

Thanks in advance

ericgibbs · Nov 13, 2008

uaefame said:
Interesting,
hi eric
you mean STATUS? or STATE because i can't find STATE in the register file map?

Thanks in advance

hi,
The STATE is used to refer to voltage level of a BIT, when its at +V its a High state and when its 0V its a Low state.

When you write the BIT pattern to the different peripheral control registers it instructs the peripheral to generate an Interrupt [or not to] when certain conditions are met.

I will not answer Pommies part as he is dealing with your program.

uaefame · Nov 18, 2008

Code:

		movfw	PCLATH
		movwf	int_pclath
		clrf	PCLATH

Sorry for keep asking questions about these codes.
Q1> PCLATH what is PCLATH?
Q2> Why we are interested in saving it value i mean stacking it up and then poping it again?

I understand that PCLATH has something to do with 2k pages? But i couldn't understand it well any help here?

Thanks in advance

Nigel Goodwin · Nov 18, 2008

As with all of your question - READ THE DATASHEET.

But in that fragment of code it's saving PCLATH so it can be restored later when the ISR exits.

BeeBop · Nov 18, 2008

uaefame said:
Code:

movfw PCLATH movwf int_pclath clrf PCLATH

Sorry for keep asking questions about these codes.
Q1> PCLATH what is PCLATH?
Q2> Why we are interested in saving it value i mean stacking it up and then poping it again?

I understand that PCLATH has something to do with 2k pages? But i couldn't understand it well any help here?

Thanks in advance

A1> Program Counter LATch High The PC is more than 8 bits wide, so these are the most significant bits of the program counter.

A2> The 'slice' of code you posted is out of context, but I'm guessing it is part of an interrupt service routine? You would want to save it as part of the context when your micro handles an interrupt so the program counter can return to where it was working before the interrupt occurred.

You should look up PCLATH in the data sheet.

uaefame · Nov 18, 2008

Thanks again,

I see why I was confused because PC is a 13bit. Usually in the manual it's written as PCL and PCH this time PCH is not used therefore i was confused and instead PCLATH is used now i understand what PCLATH is.

Ya you are right! I need to look up the manual. Sometimes you read the manual without knowing the basic is a bit confusing now things are cleared up, I will give it another try thanks again.

uaefame · Nov 18, 2008

General Question about Pommie coding

In page 5, the codes is presented. The program is Loop goto Loop. How the interrupt works? How the program know when to handle interrupt.

What I understand is:
First> In interrupt, it will stack the values of w, status and PCLATH
Second> It will check PORTB,0 if its on or off
Third> Move the value of ontime and ontime+1 to CCPR1H and CCPR1L same if it was off but the values changes
Fourth> Reset special event trigger interrupt
5th> Pop everything back
6th> Interrupt happen again Don't know how?
7th> same as 1
8th> same as 2
and the else is same the only thing I understand which is happening it is swaping everytime between on and off timing.

My main question: How it know when an interrupt happens? Does the word interrupt ring a bell in assembly language?

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