TPS6594-Q1: AMUX_OUT pin goes high when PMIC put to MCU only mode

Hello Raghavendra,

What TPS6594 part number do you have, this makes it much more clear as the PMIC states.

How are you setting AMUX_OUT low and from what state is this transitioning from?

Raghavendra Kulkarni said:

Before changing to MCU only mode, I set AMUX_OUT to low, this works. But when changed to MCU only mode, AMUX_OUT automatically goes to high. What is the reason?

Depending on the programming for the device, a possibility is that the device is hard coded to enable this resource when transitioning to MCU_ONLY mode as for many safety parts this is needed for coverage.

Raghavendra Kulkarni said:

Looks like MCU is not running after switching to MCU only mode. Does PMIC detected any errors/interrupts and move to safe state?

Depends on the SoC & TPS6594 NVM, please provided both part numbers. Yes, when fatal errors are introduced the PMIC will power down in manner reflecting the urgency, transition to safe state, and then attempt another power up. This is dependent on the part number.

Raghavendra Kulkarni said:

As JTAG connection is lost, do not know how to check what's happing in MCU. Trying to use AMUX_OUT state changes to see that MCU is working in MCU only mode. But AMUX_OUT automatically goes to high after MCU only switching and MCU is not running because, MCU cannot change the AMUX_OUT state

There are better signals to observe if the MCU is supposed to be active such as the nRSTOUT pin.

BR,

Nicholas

Thank you for the reply,

We are using 2 PMIC setup

TPS65941210-Q1  as PMIC-A and TPS65941111-Q1 as PMIC-B

AMUX_OUT from the PMIC-A is kept open and measured to check whether MCU still running when enters to MCU only mode as JTAG is lost.

nINT and END_DRV are low

nRSTOUT pin is high and nRSTOUT_SOC is low when MCU only mode is entered. 

MCU rails are active, showing correct voltages and SoC rails show zero volt in MCU only mode.

My main problem is, MCU is not running when MCU only mode is active though MCU rails seems to ON and nRSTOUT is high. 

As there are no GPIO on our board connected to MCU domain available outside, I tried to toggle AMUX_OUT to check whether MCU is active.

I am also measuring I2C data line and do not see any data being transferred from MCU once we enter MCU only mode. To debug periodically reading PMIC register to see activity on I2C. But no activity after MCU only mode.

Hello,

I read NVM registers for both PMICs,

PMIC-A

TPS65941210-Q1 => 0x48

DEV_REV => 0x82

NVM_CODE_1 => 0x10

NVM_CODE_2 => 0x04

PMIC-B

TPS65941111-Q1 => 0x4C

DEV_REV => 0x82

NVM_CODE_1 => 0x11

NVM_CODE_2 => 0x03

For the AMUX out, before MCU only mode, i set state to disabled. I can see 0V
After MCU only mode, AMUX automatically changes to close to 1.3 V

Hi,
Is there any way to still connect JTAG (Trace32) in MCU only mode? 

Hello Raghavendra,

Raghavendra Kulkarni said:

Hello,

I read NVM registers for both PMICs,

PMIC-A

TPS65941210-Q1 => 0x48

DEV_REV => 0x82

NVM_CODE_1 => 0x10

NVM_CODE_2 => 0x04

 

PMIC-B

TPS65941111-Q1 => 0x4C

DEV_REV => 0x82

NVM_CODE_1 => 0x11

Thank you, so it looks more than likely this is a TPS65941310 & TPS65941111 setup as we don't offer up a TPS65941210.

Here's a User's guide on the setup, I'll be referring to this setup: TPS65941310-Q1 and TPS65941111-Q1 PMIC User's Guide for Jacinto™ 7 J721E, PDN-0A

Raghavendra Kulkarni said:

For the AMUX out, before MCU only mode, i set state to disabled. I can see 0V
After MCU only mode, AMUX automatically changes to close to 1.3 V

A transition to MCU only mode will always enable the AMUX to output the reference voltage on the pin. This is programmed into the unit and can not be altered.

The nRSTOUT pin is the most sure fire way to tell if the power sequence has completed and all of the power rails specified to on for the MCU have been completed as it is the last resource to be asserted high.

Raghavendra Kulkarni said:

Hi,
Is there any way to still connect JTAG (Trace32) in MCU only mode? 

Raghavendra Kulkarni said:

I am trying to put PMIC to MCU only mode on our custom board

Since this is a custom board, I'm not sure of "Trace32" or the custom board's implementation of JTAG.

More over how was the MCU only mode enabled, what trigger was done to switch over to MCU only mode?

Best Regards,

Nicholas

Thank you for reply,
MCU only mode is triggered via controlling NSLEEP1 and NSLEEP2
Via I2C, address 0x86 and value 0x02 for PMIC - A (0x48)
I can see the I2C data line. When interpreted the i2C data on bus, its matching.