TCAN1145-Q1: SWE and tSILENCE

Hi Tyler,

Thank you for the clarification. Would you please check if my description that follows is true?

So the appropriate description for the sentence #1 should be “t_INACTIVE timer starts after t_SILENCE timer expires” instead of “t_SILENCE and t_INACTIVE timers start”, because they are different timers and do not start at the same time. t_INACTIVE timer here is the same as SWE timer, while t_SILENCE timer is not a part of SWE.

I would like to make it clear the explanation of 10.4.1 section, which is also very confusing. There are 2 cases of CANSLNT_SWE_DIS=”0” and “1”. The difference between them should be, in case “0” to stop the timer CANSLNT must be cleared, while in case “1” a bus activity stops the timer. Although different descriptions are applied for the start of SWE timer, they are the same because “CANSLNT interrupt is set” “when no bus activity is present for longer than t_SILENCE”. They are the same.

Now I am getting understanding the sentence #2. It should be, when SWE timer runs for t_INACTIVE without stopped by bus activity (CANSLNT_SWE_DIS=1) or clearing CANSLNT (CANSLNT_SWE_DIS=0) the device enters sleep mode. Referring SWE_DIS is wrong.

Regards,

Oguri

Hi Tyler,

Thank you again for the further clarification. I tried to make 10.4.6 section simpler and clearer as shown below. Please again confirm if it is correct. I think the section title of “SWE Timer” is more appropriate instead of “Fail-safe Features”. The descriptions for “Fail-safe Mode” should be placed right after Standby mode.:

10.4.6 SWE Timer

The sleep wake error (SWE) timer is to make the device transitions to Sleep Mode when there is no expected activity in each functional mode for t_INACTIVE (5 minutes max).

Standby Mode (transition by power up and UV_SUP event):

When rising voltage at VSUP crosses V_SUP(PU)R, the device transitions to Standby mode and SWE timer starts. Before SWE timer expires the device should be configured as Normal Mode or Listen Only Mode, or the interrupt registers for the cause of transition (PWRON in INT_2) should be cleared. Otherwise the device transitions to Sleep Mode.

Standby Mode (transition by wake up events and frame overflow):

With a wake up event or frame overflow the device transitions to Standby Mode, and SWE timer starts after t_SILENCE (1.2s max) of no bus activity. Before SWE timer expires the device should be configured as Normal Mode or Listen Only Mode, or the interrupt registers for the cause of transition (CANINT, LWU, and FRAME_OVF in INT_1) should be cleared. Otherwise the device transitions to Sleep Mode.

Normal Mode / Listen Only Mode:

In Normal Mode and Listen Only Mode, SWE timer starts after t_SILENCE (1.2s max) of no bus activity. When SWE timer expires without reset by bus activity (CANSLNT_SWE_DIS=1) or clearing CANSLNT (CANSLNT_SWE_DIS=0), the device transitions to sleep mode.

Fail-safe Mode:

When the device transitions to Fail-safe Mode, SWE timer starts. A wake event resets SWE timer, but wake events are ignored when the interrupt registers for the cause of transition (UVIO, UVCC, and TSD in INT_2) are not cleared. When SWE timer expires, the device transitions to Sleep Mode.

The SWE timer can be disabled by setting SWE_DIS; 8'h1C[7] = 1 and FS_DIS at 8'h17[0] = 1. But it cannot be disabled for power up. Figure 10-22 summarizes SWE timer.

10.4.3 Fail-safe Mode

Fail-safe mode is a low power mode the same as Standby mode the device transitions when TSD, UVCC, or UVIO happens. Wake events are ignored when the interrupt registers for the cause of transition (UVIO, UVCC, and TSD in INT_2) are not cleared. SWE timer starts at the transition. (Following is the same as the datasheet) This mode is default on and can be disabled by setting register 8'h17[0] = 1. A fail-safe mode counter is available that after a set number of events in a row the device performs the programmed action which can include going to sleep and a WUP or LWU event does not wake the device. A power on reset is required. The counter is default disabled and can be enabled at 8'h17[7]. The counter expiration action is at 8'h17[6:4]. The number of events before action is programmed is set at 8'h18[7:4] with a value up to 15 events. 8'h18[3:0] is the running up/down fail-safe event counter that can be read and cleared. If fail-safe mode is entered a global interrupt is issued, 8'h53[5] and the reason for entering fail-safe mode is provided by register 8'h17[3:1].

Regards,

Oguri

Oguri,

I don't think section 10.4.6 should be replaced with SWE timer as the section heading as this device implements many fail-safe features other than just the SWE timer. Features like sleep mode via sleep wake error or driver and receiver functionality all fall into this category.

I am trying to understand your overall motive for this question. Are you suggesting that we alter the wording in our datasheets to make data to the user more clear? 

Regards,

Tyler

Hi Tyler,

But it seems only SWE timer and some feature of Fail-safe mode are discussed in 10.4.6.

I was trying to understand the datasheet to explain how the device works for my customer. It took more than 2 months of hard work and another some hours to make the summary in the last post. I definitely believe the datasheet is impossible to understand. Please confirms if my statements are correct in last post.

By the way, however, I heard today from the customer the requirement for partial networking is deleted. So, I do not have to understand TCAN1145-Q1 right now.

Thank you.

Regards,

Oguri

Hi Tyler,

OK! Thanks. I would like to add 1 more comment. After UVSUP event, to reset SWE timer PWRON flag should be cleared. Isn't it UVSUP flag instead of PWRON?

Regards,

Oguri

Is there PWRON flag to clear in UVSUP event? I guess in UVSUP event only UVSUP flag is asserted while PWRON flag is not asserted. Thanks.

Oguri