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Outputs high to power
Hi!
I have a boards with a pic16f628a how can we ensure that the outputs go high for some fraction of a second when the power circuit?
example configuration:
@ device pic16f628A,xt_osc,wdt_on,pwrt_on,protect_off,mclr_ on,bod_Off
define osc 4
DEFINE HSER_RCSTA 90h
DEFINE HSER_TXSTA 24h
DEFINE HSER_BAUD 9600 '
DEFINE HSER_CLROERR 1
SYMBOL s2 =PORTA.0
SYMBOL s1 =PORTA.1
SYMBOL canc_2 =PORTA.2
SYMBOL stop_1 =PORTA.3
SYMBOL power =PORTA.4
SYMBOL ferma =PORTB.0
' =PORTB.1 'RX
' =PORTB.2 'TX
SYMBOL led =PORTB.3
SYMBOL canc_1 =PORTB.4
SYMBOL canale2 =PORTB.5
SYMBOL canale1 =PORTB.6
SYMBOL stop_2 =PORTB.7
cmcon=7
OPTION_REG.7=1
low canc_1
low stop_1
low canc_2
low stop_2
low led
input s1
input s2
input canale1
input canale2
input ferma
output canc_2
output stop_1
output power
output led
output canc_1
output stop_2
I can resolve this problem?
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Put an LED on your output and to ground, if it lights up, then its High!!
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Hi, Volcane
There are two things to consider :
1) at power up ... Pic acts just like if you had forgotten to place it !!! ( all ports are INPUTS )
... so, you must design your power section according to that.
2) you can program the outputs to be High, as soon as processor execute the TRIS command ( after some µsecs, then ....) :
Write :
PORTa = %11110101 ' for example
TRISA = % 00001010 ' "
Here you FIRST set the output latches in the correct state
THEN choose your I/Os.
This is THE classical "bug" for electronic ignitions ... coil is powered at poweron ... then the port is set to de-energize the coil ... results a nice "bang" or crankshaft back kick !!!
Alain
