Hello All, There is a board with BlackFin BF-537 DSP. We are not using the RTC which is built in BlackFin. I want to disable the RTC to avoid any unwanted activity. There is no way to disable the RTC by software. The RTC has the separate power supply input (VDDRTC), and the pins for connecting a 32k XTAL (RTXI and RTXO respectively). The datasheet says nothing on this matter. The customer support has no clue as usual. It seems logical to me that the VDDRTC should stay connected, and the RTXI should be pulled to the ground. What would be your opinion about that? Vladimir Vassilevsky DSP and Mixed Signal Consultant www.abvolt.com
Disable the RTC?
Started by ●September 25, 2007
Reply by ●September 25, 20072007-09-25
On Tue, 25 Sep 2007 21:09:36 -0500, Vladimir Vassilevsky wrote:> Hello All, > > There is a board with BlackFin BF-537 DSP. We are not using the RTC which is > built in BlackFin. I want to disable the RTC to avoid any unwanted activity. > There is no way to disable the RTC by software. The RTC has the separate > power supply input (VDDRTC), and the pins for connecting a 32k XTAL (RTXI > and RTXO respectively). > The datasheet says nothing on this matter. The customer support has no clue > as usual. > It seems logical to me that the VDDRTC should stay connected, and the RTXI > should be pulled to the ground. > What would be your opinion about that? >TI tech support (at least 5 years ago) was way better than that. You could tell that all the hard questions went to Hyderabad where they would be researched at $10/hour, but one generally got answers -- even to obscure questions -- in the following morning's email. At a guess, I would say you're doing the right thing, although if the RTC can be separately powered _up_ it may well be able to separately power it _down_. -- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
Reply by ●September 26, 20072007-09-26
Tim Wescott wrote:>>There is a board with BlackFin BF-537 DSP. We are not using the RTC which is >>built in BlackFin. I want to disable the RTC to avoid any unwanted activity. >>There is no way to disable the RTC by software. The RTC has the separate >>power supply input (VDDRTC), and the pins for connecting a 32k XTAL (RTXI >>and RTXO respectively). >>The datasheet says nothing on this matter. The customer support has no clue >>as usual. >>It seems logical to me that the VDDRTC should stay connected, and the RTXI >>should be pulled to the ground. >>What would be your opinion about that? >> > > TI tech support (at least 5 years ago) was way better than that. You > could tell that all the hard questions went to Hyderabad where they would > be researched at $10/hour, but one generally got answers -- even to > obscure questions -- in the following morning's email.When I asked TI about the internal structure of the TAS3004 filters, they send me to the 7th level of support (whatever it means), and then refused to disclose any details.> At a guess, I would say you're doing the right thing, although if the RTC > can be separately powered _up_ it may well be able to separately power it > _down_.OK, I found the recomendation in the hw. manual which states exactly the same thing: pull RTXI to the GND and leave the VDDRTC connected to VDD. As for the customer support, they are not supposed to know and to provide any information beyond what was already published in the manuals and appnotes. Sometimes you can get an additional information on the NDA, but only sometimes. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
