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I'm using a 16F628A which I believe should run as low as 2 volts. It works just fine from batteries providing just under 6 volts but not from 3 volts. The setup is a simple button to INT that triggers an LED to blink. Bypassing the chip and powering the LED (though the resistor) lights up the LED just fine. I figured maybe the battery didn't have enough juice, so I connected the circuit to a line power supply set at 3 volts and it didn't work. Me thinks I'm missing something here...
Thanks,
Tom
Did you also tried with the LF serie???
Did you try to disable the Brown-Out detect fuse???
F serie are suppose to work @ 3v under 10MHZ. See the Voltage-Frequency graph at the end of the datasheet.
I have a load (>10 000 units) of these F serie and LF serie on the market now running with a pair of AAA cells. No problem with them... as now...
Do you have the BOREN configuration bit set? If so, it looks like you'll be in brown out reset if you are under 3.65-4.00 volts.
I think Bob has hit on the problem. You'll need to disable BOR, and stay below 10MHz oscillator frequency to run this PIC at 3V.
Actually, I think it was race to the finish between me and mister_e based on the timestamps. He said it also..... He must type faster than me : )
hehe i had this impression of 'already said before' or "DEJA VUE' depending french ore english version you want to have.
Now that we are 3 with the same version/results... i must be true :)
I did try disabling the brown out and got interesting results. I think I mentioned above that I have a button triggering an interrupt that flashes an LED. Well, with brown out disabled, the LED constantly flashes. I don't have to press the button. (At least it runs, but not how I'd hoped.) I should have mentioned that I'm using the internal oscillator. Honestly, I'm not sure what it is running at. I think it defaults to 4MHz.
Can you post your code?
The idea is that the chip sleeps until it gets an interrupt. This all works fine with 6 volts. I'm not setting the brown out to disabled here because I have to do it via the programmer (believe me, I've tried it both ways). I also set the internal oscillator with the programmer. It only has a setting for internal with or without the clock, not a frequency.
Code:
Thanks!Code:'----------------------------------------------------------------
' includes
'----------------------------------------------------------------
Include "modedefs.bas"
'----------------------------------------------------------------
' definitions
'----------------------------------------------------------------
'----------------------------------------------------------------
' constants
'----------------------------------------------------------------
'----------------------------------------------------------------
' variables
'----------------------------------------------------------------
i var byte
'----------------------------------------------------------------
' init
'----------------------------------------------------------------
init:
' set all VARs to zero
clear
' set configuration fuses
@ DEVICE pic16F628A, WDT_OFF ' turn watchdog timer off
' set up interrupt handler
INTCON = %10010000
OPTION_REG = 0
on interrupt goto handleInterrupt
low 7
' set portb/0 to input
TRISB.0 = 1
'----------------------------------------------------------------
' main
'----------------------------------------------------------------
main:
sleep 0
pause 1
' blink an LED on pin RB7
for i = 0 to 3
high 7
pause 300
low 7
pause 300
next
goto main
'----------------------------------------------------------------
' handleInterrupt
'----------------------------------------------------------------
disable
handleInterrupt:
' globally turn off interrupts
INTCON.7 = 0
' clear the interrupt triggered flag
INTCON.1 = 0
resume
enable
END
-Tom