zigbee security link key

TC Link Key is just for ZC/ZED to transfer network Key. After ZEd joins network, it saves network Key in NV so it doesn't matter you change TC Link Key. Unless ZED needs to reassociate with ZC to get network Key.

i meant that i changed the link key before ZEd joined the network, and because ZEd and ZC have diffrent link keys i dont understand how ZED can join the network.
am i missing some thing?

Does this ZED join the same ZC network before?

yes alot of times .
do you suggest that he keeps the linked key somewhere and this is the reason why he succeeded to connect again.
if so , do you know where does the old linked key is stored?

If ZED had joined ZC, it would store network in NV. When you power recycle ZED, it won't need to exchange network key again and that's why it joins to ZC even you change TC Link Key.

do you know where he keeps the network key that he got from the coordinator?
i know that he doesnt store it in ZCD_NV_NWK_ACTIVE_KEY_INFO because i checked and after the device leaves the network this nv item is all zero's .

1. You can hard code network key to defaultKey[] in nwk_globals.c.

2. It is written to NV in zgPreconfigKeyInit() using NV ID=0x0062.

hello again ,
I did a little experiment , the ZED joined the network and then the ZC removed him from the network.
I changed only in ZC the link key and the network key and then ZC tried to discover deviced and the same device succeeded to join the network.
this is my configuration :
in ZC:
ZCD_NV_PRECFGKEYS_ENABLE = FALSE
ZCD_NV_SECURITY_MODE = 1
ZNP_NV_USE_DEFAULT_TCLK = FALSE

in the coordinator side I changed the link key in ZCD_NV_TCLK_TABLE_START nv item and the network key in ZCD_NV_NWK_ACTIVE_KEY_INFO nv item

do you have any idea how it is possible?

I am confused by your descriptions. Can you elaborate what you intend to achieve?

i want to change the link key..
i want to check that if i changed the link key in the coordinator s and in the device there will be a different link key so the device will not succeed to join the network

I am pretty sure if you use different TC Link Key on ZC and ZED, ZED won't be able to join ZC. I suggest you to erase the flash on your ZC and ZED first. Then, do the test again.

and if I didn't compile with flags TC_LINKKEY_JOIN and without SE_PROFILE the device still won't join the ZC?
maybe I don't change the right nv item?

If the device won't join, I suggest you to use Ubiqua Packet Analyzer to check it.