Thanks for that.
My original circuit had three octal darlingtons (ULN 2803) with inputs directly coupled to Ports A, C and D I have also connected leds with 680ohms to each pin so that I can see what the ports outputs are. A test program switched on and off each led in turn thru ports D C and A in that order and worked OK. Problem arose when tryin to switch on all of the A port bits and leave them on. I have now disconnected ther darlington from port a and written the following simple test program:
I have just run this program andCode:@ DEVICE pic16f887,intrc_osc_noclkout PORTD = 0 PORTA = 0 PORTC = 0 TRISD = 0 TRISA = 0 TRISC = 0 portA.0 = 1 pause 500 porta.1 = 1 pause 500 porta.2 =1 pause 500 porta.3 = 1 pause 500 porta.4 = 1 pause 500 porta.5 = 1 pause 500 porta.6 = 1 pause 500 porta.7 = 1 end
1. When Microcode studio fired up the Pickit2 the voltage Vdd had been set down to 3.3
2. I turned up Vdd to 5 volts and programmed the chip.
LEDs 0,1,2,3 tuswitched on and then off after the delay. LED 4 switched on and stayed on, LED 5 switched on and then off again after the delay and then LEDs 6 and seven switched on and remainedon. I can see no logic inthis although I have that horrible feeling that it is staring me in the face !






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