Power up problem with PIC16F1824

[nobner]

Hello together,
i have a problem with powering up a PIC16F1824.
When I apply 5V, the port RA5 gets high for 1µs.
Power Supply is fine, no interruptions - 100n directly on controller supply pin's.
On the port I have connected a FET (resistor 1K from port to gate, 47k from gate to gnd)
I defined port as output in tris register.
Power up timer is enabled.
In a former thread i read, that port and lat settings must be done before tris setting - so
I did this, but the 1µs pulse is still there.
I tried lata and porta - no difference.
I would be thankful for any idea.
best regards
norbert

[longpole001]

you do not say if the fet is PCh or N ch , but have you tried clearing the port after after assigning the TRIS register . It be helpfull if you included the area of code that you use to configthe chip , assuming its not changed on the fly in other parts of the code

this for the PIC 16F1825 , so should be trhe same for your pic



' config for 16F1825

#CONFIG
;----- CONFIG1 Options --------------------------------------------------
__config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_ON & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_ON

;----- CONFIG2 Options --------------------------------------------------
__config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_HI & _LVP_OFF
#ENDCONFIG



'----------- 16F1825 - PIC chip settings --------------------

OSCCON = $70 ' Select 32Mhz , internal clock ( 8Mhz when conf2 - PLLEN_OFF)
' Bit 7 0 = 4xPLL disabled 1= 4xPLL enables ( overrided by conf word 2 setting - PLLEN)
' bits6-3 - 1111 = 16Mhz , 1110 = 8MHz or 32Mhz ( depends on 4xPLL - conf word 2) 1101 = 4 MHz, 1100 = 2MHz 1011 = 1MHz
' bitS 0-1 - 00= Clock set by Conf word ,01 = Timer1 OSC , 1x = internal Osc Block

APFCON0 = %00000000 ' All Default - No change when using SPI use SDO1 = RC2 , bit6=0
APFCON1 = %00000000 ' All Default APFCON1 = %00000000



CM1CON0 = $00 ' Disable / Clear comparator 1
CM1CON1 = $00 ' Used with CM1CON0
CM2CON0 = $00 ' Disable / Clear comparator 2
CM2CON1 = $00 ' Used with CM2CON0
CMOUT = $00 ' Disable Comparitors output register - used only if comparitor on

ANSELA = %00000000 ' Set Port A - Digital I/O , 0 = Digital 1 = Analog
ANSELC = %00000000 ' Set Port C - Digital I/O , 0 = Digital 1 = Analog

INLVLA = %00000000 ' Set Port A to TTL Levels 0 = TTL , 1 = SCHMITT TRIGGER - Used port reads and Interupt on Change
INLVLC = %00000000 ' Set Port C to TTL Levels 0 = TTL , 1 = SCHMITT TRIGGER - Used port reads and Interupt on Change
SRCON0 = %00000000 ' Disable Latched Outputs
SRCON1 = %00000000 ' Used with SRCON0 register

ADCON0 = $00 ' Disable A/D
ADCON1 = $00 ' Disable A/D - used with ADCON0 settings

WPUA = %00001000 ' Port A - Turn off week Pullups 1=ON , for each port ( globle enable set in option_reg.7)set wpu on PortA.3 as input only - ref spec
WPUC = %00000000 ' Port C - Turn off week Pullups 1=ON For each port

DACCON0 = $00 ' Disable D/A
DACCON1 = $00 ' Disable D/A - used with DACCON0
FVRCON = $00 ' Disable Fixed Voltage Ref


OPTION_REG.7 = 1 ' Weak Pullups disabled 1 = globel disable 0 = globel enable ( set by each port - WPUA & WPUC settings)
OPTION_REG.6 = 0 ' Interupt on Falling Edge of INT pin 0= falling edge 1= rising edge
OPTION_REG.5 = 0 ' TMR0 clock source - 1=T0clk pin 0=internal clock
OPTION_REG.4 = 0 ' TMR0 0=L/H of TOCKI pin 1=H/L of TOCKI pin
OPTION_REG.3 = 0 ' Use Prescaller for TMR0 0= Yes , 1 = No
OPTION_REG.2 = 1 ' Timer0 prescaler Rate Select bits 2-0(set to 1:256)
OPTION_REG.1 = 1 ' 000 = 1:2 , 001= 1:4 , 010 = 1:8 , 011 = 1:16
OPTION_REG.0 = 1 ' 100 = 1:32 , 101 = 1:64, 110 = 1:128 , 111 = 1:256

T1CON = %01110100 ' Timer 1 ,bit7-6 = TMR1 CLK source 00 = Instuction Clk(Fosc/4),01 =sys clk,10=ext clk,11=cap sense osc
' bit5-4 = TMR1 prescale 11= 1:8 ,bit3=0 LP off,bit2=1 no sync ext CLK ,bit1= 0 n/a,Bit0=0 Timer 1 on/off
T1GCON = %00000000 ' Timer 1 Gate Control bit7 0= counts regardless of gate 1 = gates in use , bit6 gate active when 1= High ,0=low
' bit5 0= toggle mode diabled 1= enabled bit4 single pulse mode 1- en 0= dis, bit 2 -status bit,1-0 - gate source sel

T2CON = %01110011 ' Timer 2 off + 1:15 postscale ,1:64 prescale ( bit 7 = x, bit6-3 1110 = 1:15 postscale, bit2=0 timer off ,bit1-0 = prescale 10 = 16 , 11= prescale 64
T4CON = %00000000 ' POSTSCALER 1/1,STOP,PRESCALER 1/1
T6CON = %00000000 ' POSTSCALER 1/1,STOP,PRESCALER 1/1

TMR0 = 0 ' Clear TMR0 MODULE REGISTER

TMR1H = 0 ' CLEAR TMR1H MODULE REGISTER
TMR1L = 0 ' CLEAR TMR1L MODULE REGISTER

TMR2 = 0 ' CLEAR TMR2 MODULE REGISTER
TMR4 = 0 ' CLEAR TMR4 MODULE REGISTER
TMR6 = 0 ' CLEAR TMR6 MODULE REGISTER

'PR2 = 255 ' Timer 2 Preload value
'PR4 = 255 ' Timer 4 Preload value
'PR6 = 255 ' Timer 6 Preload value






TRISA = %00001000 ' setup Port A input=1,output=0 for I/O pins ( Note RA3 - input only - refer spec)
TRISC = %00000000 ' setup Port C input=1,output=0 for I/O pins
PORTA = %00000000 ' clear
PORTC = %00000000 ' clear

[peterdeco1]

Just throwing in my 2 cents, I had the same problem with a 16F819. I forget the port pin involved but it was connected to a piezo buzzer. Everytime the PIC was powered up it would cause a chirp in the buzzer. Turning off the power-up timer cured the problem.