MSP4305522 - questions on Port J

Brent Huebert

Expert 1140 points

In our application we’ve set up Port J of our MSP4305522 as such:

// Port J

PJREN = 0x0E; // Set PJ1-PJ3 pullups

PJDIR = 0x01; // Set PJ0 to be an output, the rest to be inputs

PJOUT = 0x0E; // Set PJ1-PJ3 pullups, and PJ0 low

Taking a look at the SYSJTAGPIN bit of the SYSCTL register with an emulator showed it to be zero. I'm wondering why the PortJ pins look low with a DVM after they are configured this way.

over 14 years ago

0 old_cow_yellow over 14 years ago

Guru 58965 points

Those pins are shared with JTAG pins. Are you using JTAG? Is the TEST pin high?

0 Brent Huebert over 14 years ago in reply to old_cow_yellow

Expert 1140 points

We do use JTAG. The pin is left floating. One of the guys here found the following, seemingly related, post that was never answered. I wonder if his issue was resolved:

http://e2e.ti.com/support/microcontrollers/msp43016-bit_ultra-low_power_mcus/f/166/t/47694.aspx

0 old_cow_yellow over 14 years ago in reply to Brent Huebert

Guru 58965 points

If you are using JTAG, the TEST pin must be connected to the JTAG-tool. If it is the "4-wire" JTAG, then the PortJ pins must also be connected to the JTAG-tool and your code cannot control PortJ.

0 Clinton Rodgers over 14 years ago in reply to Brent Huebert

TI__Genius 13235 points

Hi Brent,

Did old_cow_yellow's feedback answer your question?

Thanks,

Clinton

0 Brent Huebert over 14 years ago in reply to Clinton Rodgers

Expert 1140 points

No. I may not have posed my question very well. We've dedicated Port J to a JTAG emulator. My original question maybe should have stated we were checking voltage levels on Port J with a DMV--no emulator attached--and were surprised at the levels we were seeing on some the pins.

0 old_cow_yellow over 14 years ago in reply to Brent Huebert

Guru 58965 points

Try this:

void main ( void )
{
WDTCTL = WDTPW | WDTHOLD;
PJOUT = 0;
PJDIR = 0xE;
PJREN = 1;
while (1)
{
PJOUT ^= 8;
}
}

Download it to the chip (with JTAG tool if you want.)

Power down, disconnect all connections to JTAG, RST, and TEST.

Power up, DVM or scope Port-J. PJ.0 should be 0V (pulled down). PJ.1 and PJ.2 should be ~3V (driven high), PJ.3 should be flipping between 0V and ~3V.

0 Brent Huebert over 14 years ago in reply to old_cow_yellow

Expert 1140 points

Thanks. I think this will get us where we need to go next. Appreciate the help.

0 Omri Almog over 13 years ago in reply to old_cow_yellow

Prodigy 170 points

Hello old_cow_yellow,

I was wondering why you have PJ.1 and PJ.2 being high, when you set PJOUT = 0; Does that mean they will be driven low?

Thanks,

-Omri

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MSP4305522 - questions on Port J