XTS5000 Key retention

[superfreak]

Does the CMOS battery on the controller board support the encryption key retention in the portables. I can't find any narrative in the service manuals. The mobiles list a source of KG_Backup to the UCM which I assume is some sort of battery as well.

I am assuming that those batteries are going bad if the radio is loosing keys (And of course infinite key retention is checked in CPS)...

How long does an XTL retain keys without B+ being connected? Does it have the same sort of battery? I see references of 3day key retention. I assume that implies that a radio sitting on shelf will lose keys after 3+ days? Or more importantly if the transceiver deck is powered off a charge guard, it will lose keys if the car isn't started every three days. I am thinking that we need to make the case to bypass charge guards on the transceivers (Control head red and transceiver red MUST go to constant battery) to eliminate key loss..

 

[rescue161]

If infinite key retention is checked, the UCM can be completely removed from the radio and it will retain the key. I have done this before when I didn't have access to a keyload cable for the XTL, but did for the XTS, so I loaded a key into the portable, made sure infinite key retention was checked and then moved the UCM to the mobile and all was well.

 

[MTS2000des]

The CMOS battery is only for the clock. I have cache radios with UCMs that get stored without batteries for months and with IKR selected, they retain the keys just fine.

 

[superfreak]

So why does the XTL interface board need a capacitor/battery if they are the same UCM? How does the UCM function different;y in a portable vs mobile for key retention? Serious question... I am talking about the board mounted watch battery, not the main radio battery.

My hypothesis is that the XTS button batteries have failed (10+ years old)... Same flash/UCM/firmware everything in 4000+ portables. failure rate of key retention is 200+portable radios.

Here is the language from the XTL manual
3.8.3Encryption Voltages The secure interface board produces two voltages sourced by A+ and SW_B+ through J0501, pins 10 and 9, that are used by the encryption module: UNSW_B+_ENC (7 V) and SW_B+_ENC (7 V). The constant 7 V is generated using U800, Q802, and Q803 and is fed to J0701. At the secure interface board, the 7 V provides continuous unswitched voltage when the vehicular battery is connected to the radio and is also switched to provide SWB+ to the encryption module. A 5-V storage circuit, C810 (0.47-farad capacitor), provides +5 Vdc to the encryption module via J0701, pin 12, to hold encryption keys for a period of three days with no A+ voltage present. The 5 V and 2.85 V controller supplies are used to provide logic translation between the legacy keyloader data (5 V) and the universal crypto module (UCM) (3 V). The secure interface board also supplies the UCM chip-select logic line and the other control lines, clocks, and other components, to the main board microprocessor.

 

[MTS2000des]

Interesting. I store the XTS5000s with the batteries off (as they're maintained in gang chargers) and have never lost a key. All of them are at least a decade old. AFAIK the coin cells have NEVER been replaced. It could be that the batteries are in good shape and thus, the current drain is so low that they hold up. But we are also phasing out these legacy radios. I'll go pull some and see- last time they got used was during Super Bowl 53.

 

[rescue161]

It has to do with the Infinite Key Retention. As far as I can tell, the battery on the XTL board is for when Infinite Key Retention is not used and power from the vehicle battery is removed from the radio, the battery on the UCM board holds the key for up to 3 days. If IKR is used, the battery is not needed.

We have tons of XTS2500s that are stored for temp use and they retain the keys for years without power. The same was true for the XTL5000 and the XTS5000 when we used them.