How long does it take to disable a AM3358 module?

Chris Kessell

Other Parts Discussed in Thread: AM3358

I'm working on some safety-critical code for the AM3358 which demands that all unused modules and functions in the processor (even ones that are disabled by default) shall be explicitly disabled. That covers everything from the SGX and PRU-ICSS modules down to UARTs and Timers.

The general technique we're using is to set the Mode (MODULEMODE) field in a module's CLKCTRL register to Disabled and then wait for the Idle Status (IDLEST) field to read Disabled. This led to the question of how long the process should take.

Assuming a module is enabled, how long should it take from setting MODULEMODE to Disabled until the status changes from Functional to Disabled? Does the status change immediately or can it take a significant period of time, particularly for the more complex modules?

Thanks.

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Hi Chris,

There are latencies over the interconnects to be taken into account too. This cannot be answered in general. What do you mean by " significant period of time"? And what software are you using?

0 Chris Kessell over 10 years ago in reply to Biser Gatchev-XID

Intellectual 260 points

Hi Biser,

Sorry I wasn't clearer. All I meant was will the IDLEST effectively change state immediately (i.e. so it could theoretically be read and tested in the next instruction) or should we delay for a number of clock cycles between writing MODULEMODE and reading back IDLEST?

We're programming the AM3358 using CCS v5.2.

Thanks,

Chris

0 Biser Gatchev-XID over 10 years ago in reply to Chris Kessell

TI__Guru**** 393215 points

Certainly it will take some time, MPU clock is much faster than the L3 and L4 interconnect clock (200MHz resp. 100MHz).

0 Chris Kessell over 10 years ago in reply to Biser Gatchev-XID

Intellectual 260 points

That's understood. Will a module typically disable within, say, a few cycles of the relevant clock or can some modules take a lot longer? Is any data available concerning the enable/disable times of each type of module?

0 Biser Gatchev-XID over 10 years ago in reply to Chris Kessell

TI__Guru**** 393215 points

I'm sorry, I don't have precise data about latencies over the AM335X interconnects. On similar processors these latencies vary from 3 to 20 interconnect clock cycles.

Processors

Processors forum

How long does it take to disable a AM3358 module?