What Is the Maximum Wake-Up Interrupt Time Possible for the PWU on the NTM88Kxx5S?

[israelfelix]

Hello,

I am using the NTM88Kxx5S tire pressure monitoring sensor and I would like to understand the maximum possible wake-up interrupt time that can be configured using the Periodic Wake-Up (PWU) timer.

According to the documentation (UM11227), the PWUCS0 register allows configuring the WUT[7:0] bits up to the value of 255, and the WDIV[7:0] bits can also be set up to 255. Based on my calculations:

• WCLK (with WDIV = 255) results in a time of: WCLK=(255+1)×0.504 seconds=256×0.504 seconds=129.024 seconds
• RCLK (with WUT = 255) results in a maximum time of: RCLK=129.024 seconds×255=32,903.04 seconds

This equates to approximately 9 hours and 8 minutes.

I would like to confirm if this is indeed the maximum wake-up interrupt time achievable with the PWU on the NTM88Kxx5S or if there are any other factors that could increase or limit this time.

Thank you!

[JozefKozon · Accepted solution]

Hello Israel,

please refer to the Table 74. in the UM11227. The WCLK can be set by the WDIV bits from 0.504s to 4.584s. The 129.024s is too high value.

If the WDIV bits are set 0, the WCLK will be 0.504s. And if to 255=0xff, then it will be 4.584s.

fLFO=1000Hz

WDIV=0

WCLK=(504+16*0)/1000=504/1000=0.504s

WDIV=255

WCLK=(504+16*255)/1000=(504+4080)/1000=4584/1000=4.584s

Then you can select the number of RCLK wake-up clock till next interrupt is generated. 

You can set it from 0.504s minimally to maximally 1168.92s. The highest value equals to approximately 19 minutes and 29 seconds. 

With Best Regards,

Jozef