TPS23881: Setting/Changing PCut for pre.btclass5 device (manual mode)

Anssi Nikula

Part Number: TPS23881

Tool/software:

Hello,
I believe I have managed to setup TPS23881 into (manual) mode that seem to be compatible with MAX5982A EVKIT ( which is in pre.bt class5 mode).

Below is a dump from serial terminal (pre.bt class -eval card on port-1, class8 cards on port-2, port-3 and port-8 ), the CLASS_OVERCURRENT event caused by pre.bt class5 eval card being plugged into port-1 and based on that that port is turned into manual mode and port enabled (I tried follow TI's application note "[FAQ] TPS23881: Is the TPS23881 interoperable with non-compliant "Class 5" devices that were designed to receive >25.5W prior to the IEEE 802.3bt standard?").

CLASS_OVERCURRENT
PW EN event
PW GD event
PowEnable(0x19): 0F03000C
PowerGood(0x19): 0F03000C
...
The issue is that despite of value 0x67 (103 -> 51W) set in PCut -register , I seem to hit some (power) limit as I increase external load hooked up to Eval card's output pins, tripping around 38W (plus whatever is power consumption by eval card itself), so total probably being around +40W.
4-Pair Police(0x2A/0x2B): 67 C0 C0 FF FF FF FF C0

Class8 devices seem to response to these elevated PCut values (0xC0), but here auto-mode used and new PCut values set some time after Power Enabled -bit set.

What setting am I missing in manual mode in order to set working PCut values, should I use MPOL-bits and set PCut prior to turning Port ON ?

BR,
Anssi

over 1 year ago

0 Brandon Beader over 1 year ago

TI__Genius 15275 points

Hi Anssi,

Can you confirm you are loading SRAM to TPS23881? Check register 0x41 for the FW version.

If you can provide a register dump it would quickly expedite the debug effort here, however my guess since you are operating in manual mode, you have not overwritten the 2-Pair policing registers.

The main registers we need to take a look at include the event registers which will tell us specifically what is happening when power is turned off (Registers 02h-0Bh). The non-standard Class 5 is known as UPoE. Here are some steps for how to implement UPoE:

Load SRAM (v15)
Configure your HW setup (mostly set your port power allocation settings and device mapping settings if any
1. Register 0x29 – Port Power Allocation should be set to 4-pair 60W (0xDD) do NOT set to 2-pair 30W config
2. Register 0x26 is port remapping if the HW channels need to be remapped compared with logical channels (Should be default setting)
3. Set 4-Pair Fault Configuration Register (I recommend setting 0xFF to this register to enable 4-Pair policing settings as these will be needed for UPoE, however this is up to your system, the default value is 0x0C which is sufficient for operation).
Set Power Off to all ports Register 0x19 (Value 0x00)
Set Ports to Semi-Auto mode Register 0x12 (Value 0xAA)
Enable Classification & Detection Register 0x14 (Value 0xFF)
Monitor detection/classification results. (This will be your monitor loop for getting classification status)
Set Foldback and MPOL bits Register 0x40 (Value 0xFF)
Enable alternative foldback curves Register 0x55 (0xFF)
Adjust 4-Pair and 2-Pair Pcut thresholds
1. 4-Pair Pcut threshold Registers 2Ah – 2Bh (Values should be 60W for UPoE which equates to 0x78 for both ports, adjust accordingly)/
2. 2-Pair Pcut thresholds Registers 1Eh – 21h (Values should be up to your system if you want to limit the power per channel. For UPoE the easiest method is to match your 4-Pair and 2-Pair Pcut thresholds, but you could have some load balancing and set the 2-Pair pcut thresholds to 45W. I will leave that up to you)
If the Valid classification result, power on the port Register 0x19 (Value 0x3C). Ensure both channels connected to the port are powered on at the same time. This should always occur for Class 4 devices.)
UPoE enabled

I believe the only step you are missing is your 2-Pair PCUT value which seems to be tripping. Please make sure you set registers 1Eh - 21h accordingly. OR you can disable 2-Pair PCUT all together using register 15h.

Regards,

Brandon

0 Anssi Nikula over 1 year ago in reply to Brandon Beader

Prodigy 10 points

Thanks Brandon for detailed DO-TO list ... although I was a bit picky, I just might have now working solution for pre.bt.class5.

I had already on monday tried to use MPOL approach and set PCut values before powerinf up port/channels but I didn't realize to set foldback bits. Without those bits it does not work.

I enabled earlier a channel at the time and don't see much difference in operation whether to do it at once or one at the time. Now doing it both channels at once as you suggested.

One more question, when I keep increasing a load ( external load connected to output pins of MAX5982A EVKIT) and I approach 55W, I start seeing plenty of 4-Pair PCut -events but no output tripping. And 4-Pair Pcut limit set to 60W, but I think ~55W limit, where start seeing PCut events, is quite fine as, evaluation cards consumes some power too (perhaps around 10%)

Does this mean, now as in "manual/diagnostic" mode, there is no automatic tripping but I need to power down port/channels "manually" , as I did power up them manually as well?

Although it seems to now work, I attached log file just in case. Not quite all registers included that you requested but a good bunch of them. PCut-event priting included as well.

Regards,
Anssi

Fullscreen non-Comp-class5-B.txt Download

SRAM Code Load Complete, PSE-00 v03
SRAM Code Load Complete, PSE-01 v03
2-Pair Police(0x1E..):	FF FF FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	FF FF FF FF_FF FF FF FF
Detection event for dev/port=: 00/01=04
Detection event for dev/port=: 00/02=04
Req/Ass Class dev/port=class/class
00/01=07/00
CLASS_OVERCURRENT
Start Fault Dev/Ch:00/01
Start Fault Dev/Ch:00/02
Detection event for dev/port=: 00/01=03
Req/Ass Class dev/port=class/class
00/01=07/00
CLASS_OVERCURRENT
PowerEnable(0x19):	00000000
PowerGood(0x19):	00000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
Detection event for dev/port=: 00/02=05
PW EN event
Pcut Set:7F/00
Pcut Set:7F/00
PW GD event
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
4P PCUT Fault Channel 12:00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00
PowerEnable(0x19):	03000000
PowerGood(0x19):	03000000
FaultRegs:(0x2D):	00000000
FB-reg(0x40):	30 00 00 00
2-Pair Police(0x1E..):	5A 5A FF FF_FF FF FF FF_FF FF FF FF_FF FF FF FF
4-Pair Police(0x2A/0x2B):	78 00 FF 00_FF 00 FF 00

0 Brandon Beader over 1 year ago in reply to Anssi Nikula

TI__Genius 15275 points

Hi Anssi,

You will need to see how much power the device is actually pulling. Just to clarify, you draw >60W on the PSE but do not see the port shut off or any PCUT fault event occur? Assuming PD & DCDC loss + cable loss pulling 55W on the far end should be >60W triggering PCUT. There is also a 5% error margin the PCUT policing as well.

Since you are in manual mode, you will also need to make sure all your policing register settings are correct since nothing will be done with the PSE automatically. The above steps assume you are in semi-auto mode, not manual mode.

Please check register 2Dh settings: The bit 4PPCTnn need to be set in order for the 4-Pair PCUT to work.

b00001111 should be the correct setting -> 0x0F

Regards,

Brandon

Power management

Power management forum

TPS23881: Setting/Changing PCut for pre.btclass5 device (manual mode)