Need help for PIC16C745

[christina86]

Hi everybody,

I'm using the PIC16C745 microchip to do my final year project
the situation is, if switch 1 is pressed, LED will light up and when switch 2 is pressed again, the LED will go off. I am using an assembly language ( sofware MPLab version 7.2) to write the code. I have encounter some problem, when i apply the 5 V to the circuit. The Led must Light up, but it did not .
Here is myCode:

MAIN org 00000030h

Start
bsf STATUS,RP0 ; select bank1
clrf PORTB ; clear PORTB output latch
movlw b'00000110' ; Set all pins PORTB 1,2 as Input
MOVWF TRISB ;

ON
btfsc PORTB,1 ; Has S2 been press? (Normally high,goes low when pressed.)
goto ON ; No, go back check again
movlw b'00000001' ; move it from register 1 to w.
movwf PORTB ; move it to PORTB to light up the LED

OFF
btfsc PORTB,2 ; Has key been press? (Normally high, goes low when pressed.)
goto OFF ; No, check again
movlw b'00000000' ; move it from register 1 to w.
movwf PORTB ; OFF the LED

DebounceA
btfss PORTB,1 ; Has key been released?
goto DebounceA ; No, wait again
goto Start ; Loop again
end ; directive indicates end of code

I use only one port instead to be an input and output. When i build the code inside the PIC16C745, the Led still not turn on. Can you help me to see weather to code i have done correctly. Thank you

[Archangel]

Hi christina86,
Certainly I am not the one to ask about assembly language. That said, it looks to me like your sub routines get locked into a loop and never finish their execution.
example<p>
ON
btfsc PORTB,1 ; Has S2 been press? (Normally high,goes low when pressed.)
goto ON ; No, <font color=red> goto ON and repeats forever</font color>
movlw b'00000001' ; move it from register 1 to w.
movwf PORTB ; move it to PORTB to light up the LED<p>
I think if you wish to recheck the first line you should use whatever assembly equiv. of a for next loop.
JS

[paul borgmeier]

Hi Christina86,

This is a BASIC language forum ... ASM help is harder to get here. A quick look at your program......

See Table 4.2 in the 16F745 datasheet. You will see that PORTB resides in BANK0 and TRISB resides in BANK1.

When you want to work with PORTB, you need to make sure you are in BANK0 (clear RP0 and RP1 in the STATUS register)

When you want to work with TRISB, you need to make sure you are in BANK1 (set RB0 as you did)

If you want to continue on and change PORTB values, you need to switch back to BANK0 before updating PORTB (otherwise you will actually update TRISB even though you told the program to update PORTB)

Start 
	clrf PORTB ; STATUS defaults to BANK0 - clear PORTB output latch  (not really a latch)
	bsf STATUS, RP0 ; select bank1 
	movlw b'00000110' ; Set all pins PORTB 1,2 as Input 
	MOVWF TRISB ; 
	bcf STATUS, RP0 ; go back to  Bank 0

The 16C745 appears to be an interesting chip – I hope you are using the windowed version.

Being that this is a BASIC forum, I should tell you that what you are trying to do would be trivial with PicBasic or PicBasic Pro

Good Luck

[paul borgmeier]

Hi Joe

      btfsc PORTB,1

this command says "bit test file skip if clear" ... it jumps (skips) over the goto is PORTB.1 = 0

[paul borgmeier]

Hey Joe,

I should note that the last time you and I tried to help someone together, we got locked up and whipped ... we better tread carefully here

http://www.picbasic.co.uk/forum/showthread.php?t=6783

[christina86]

Hi Paul and Joe,

Thank you so mush for replying my post. I am totally new to this PIC16C745, i have got the project from my teacher which is totaly new to me, it is nothing related to my course of study. I am in the process of learning. Please give me your guidance.
I have made some changes to the code but it is still not working . Can you help me to check?
The code is :
AIN org 00000030h

Start
bsf STATUS,RP0 ; select bank1
movlw b'00000110' ; Set pins PORTB 1,2 as Input
movwf TRISB ;
bcf STATUS, RP0 ; go back to Bank 0
ON
btfss PORTB,1 ; Has S1 been press? (Normally high,goes low when pressed.)
goto ON ; No, go back check again
movlw b'00000001' ; move it from register 1 to w.
movwf PORTB ; move it to PORTB to light up the LED

OFF
btfss PORTB,2 ; Has key been press? (Normally high, goes low when pressed.)
goto OFF ; No, check again
movlw b'00000000' ; move it from register 1 to w.
movwf PORTB ; OFF the LED

end ; directive indicates end of code
Thank you Paul and Joe so much . I look forward to hearing from you.

[Archangel]

Hey Joe,

I should note that the last time you and I tried to help someone together, we got locked up and whipped ... we better tread carefully here

http://www.picbasic.co.uk/forum/showthread.php?t=6783

Yes, We were spanked ! I think this poor kid is going to have to repeat this class, I just looked at the .lst file for a simple "Blinky" and it was 57k file size, I have just downloaded Section 29 from Microchip website.
Christina, here is a forum from Microchip, where they speak assembly, and apparently C as well.:
http://forum.microchip.com/tt.aspx?forumid=-2