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Problem with msp430F2618

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Member level 5
Aug 24, 2006
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I am facing the problemlast from last few days. I have tried many options but in vain.

Set up:
I am using MSP - FET430UIF as emulator device. The device is installed properly.
I am using IAR version 5.30(FET_R520.exe).
Evaluation Board of MSP430F2618(64 pin) having code below mentioned.
I am just togging one port pin P4.0.
On giving supply of 3.4V through capacitors to AVCC and DVCC pin, I am getting proper toggling on pin.

If I disconnect the supply and giving pull up of 10K with 3.4V supply on port pin P1.5.
I am getting 2 V on AVCC and DVCC pins of microcontroller because of that my controller is getting On and toggling is still present there.

NOTE: Supply is disconnected even after that I am getting 2V on supply pins by giving supply of 3.4V on one port pin.

Software Code:

int main( void )
// Stop watchdog timer to prevent time out reset

P1DIR |= 0xFF;
P2DIR |= 0xFF;
P3DIR |= 0xFF;
P4DIR |= 0xFF;
P5DIR |= 0xFF;
P6DIR |= 0xFF;

/* Set all port as Low */

P1OUT = 0X00;
P2OUT = 0X00;
P3OUT = 0x00;
P4OUT = 0x00;
P5OUT = 0x00;
P6OUT = 0x00;

P1SEL &= ~0x020; // Set P1.5 to input direction for sync pulse interrupt

P1DIR &= ~0x020; // Set P1.5 to input direction for sync pulse interrupt

P1REN |= 0x020; // P1.5 interrupt enabled

P1OUT &= ~0x020; // Set P1.5 to input direction for sync pulse interrupt

P4OUT ^= 0x01; // Gain selection
for(g_uiAmpFactor = RESET; g_uiAmpFactor < 50000 ; g_uiAmpFactor++);



What did you expect?
Most of the port pins are connected internally via diodes to GND and VDD for protection purposes. When the potential of the port pin is under GND, or above VDD (with approximately 0.6V), one of the 2 diodes begins conducting in trying to equalize the 2 potentials.

In your case is like supplying the uC through the pull-up and port pin and this is a faulty design, because VDD & GND are the last signals in a circuit to be "disconnected" from the power supply.
This is not only annoying, but it could also destroy the internal diode (at least) if the current through it is big enough.

Correct this by tying the pins via pull-ups (pull-down's) to uC's VDD (GND) signal(s) and not separately to the power supply. Then you connect this "power-plane" to the power supply, so that everything gets "disconnected" at the same time (VDD and ports alike).



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