AM5748: WD timers clock source

Jimmy Kjellsson

Part Number: AM5748

)Hi,

As i have understood it there are two possible sources in the AM5748 which can be used to implement watchdog functionallity in the A15 cluster.

1: MPU_WD_TIMER, which has two channels

2: WD_TIMER2

As far as I can read the TRM the MPU_WD_TIMER will use the same main clock source which is used for creating the A15 main clock (in my case derived from the OSC0 20MHz input oscillator) is this correct? Is this also true for WD_TIMER2?

In summary, my question is: Is it possible to source either MPU_WD_TIMER or WD_TIMER2 from another clock-source than whats used to clock the a15 core complex, e.g. OSC1 when OSC0 is used as main clock input? Reason for asking is that I want to implement an independent watchdog which would react e.g. if main oscillator fails.

BR Jimmy

over 6 years ago

0 Biser Gatchev-XID over 6 years ago

TI__Guru**** 393215 points

Hi,

WD_TIMER2 functional clock is sourced from the 32kHz system clock, as explained in section 22.4.1 of the AM574x TRM Rev. A. This cannot be changed.
The MPU_WD_TIMER functional clock is sourced from the MPU_DPLL_CLK through a prescaler. See Table 4-98 in the TRM for details.
To summarize, clock sources for all WD timers are fixed and cannot be changed.

0 Jimmy Kjellsson over 6 years ago in reply to Biser Gatchev-XID

Prodigy 170 points

Hi,

Thanks for the fast response!

I then have one follow up question, as you say, in 22.4.1 it is stated that "the 32kHz clock" is used for the WD_TIMER2, but is that FUNC_32K_CLK, which is derived from SYS_CLK1 or is that OSC_32K_CLK which is derived from the on-chip RC-oscillator?

BR Jimmy

0 Tom Johnson 16214 over 6 years ago in reply to Jimmy Kjellsson

TI__Mastermind 46460 points

Jimmy,

We apologize for the delay. Yesterday was a holiday in the US and we were not been able to determine a concise answer on Friday. In multiple places the TRM stated that FUNC_32K_CLK comes from SYSCLK1/610 which comes form the OSC0. The footnote (1) under Table 5-6 in the Data Manual is the only place that indicates that there is an alternative clock source. We are working to validate this.

Tom

0 Jimmy Kjellsson over 6 years ago in reply to Tom Johnson 16214

Prodigy 170 points

Hi Tom,

Thank you for the response, until final verification from you i will then assume that there are no possibillity for a independently clocked WDT in the AM5748.

BR Jimmy

0 Tom Johnson 16214 over 6 years ago in reply to Jimmy Kjellsson

TI__Mastermind 46460 points

Jimmy,

That is the best assumption. FUNC_32K_CLK comes from SYSCLK1/610 which comes form the OSC0. It appears that the design allowed for an alternate clock source at one time but that the alternate source was deprecated from the documentation due to a design limitation. We will remove the footnote from the Data Manual.

Tom