LS1088A Thermal problem (-40 Degree)

[MustafaOguz]

Hi,

We are using "LS1088AXE7MQA" CPU in our board. We powered our board at -40 Degree. Device boot itself at -40 degree and during 1-2 hours,  It's functions run correctly (clocks and powers are also all stable) however after 1-2 hours, LS1088 assertes a reset request from its "RESET_REQ_B" pin and CPU resets itself and the boot sequance restarts. After reboot sequence complated, CPU again starts working correctly. However, this can be happen periodically eg in every  1-2 hours. We turned off thermal management unit (TMU) inside the chip. Turning off TMU made device more stable at -40 degree however, we can still encounter this reboot problem periodically eg 3-4 hours after TMU is disabled. What are the possible reasons that cause this fault ? In which conditions does LS1088AXE7MQA assert reset request?  I also wrote down our RCW datas : 

Reset Configuration Word (RCW):
00000000: 30004014 00000030 00000000 00000000
00000010: 00000000 000a0000 00300000 00000000
00000020: 016011a0 00002580 00000000 00000000
00000030: 0000004b 00000000 00002403 00000000
00000040: 00000000 00000000 00000000 00000000
00000050: 00000000 00000000 00000000 00000000
00000060: 00000000 00000000 00000009 000009e7
00000070: 33110004 00006050
 

You can also find the attached block diagram of the design.

Best Regards, 

Mustafa Oguz Donmez.

[ufedor]

To determine RESET_REQ_B cause:

1) Disable PORESET_B assertion in response to RESET_REQ_B assertion.

2) After RESET_REQ_B assertion execute following commands in the ccs (CodeWarrior Connection Server) console:

delete all

config cc cwtap

ccs::config_chain {ls1088a sap2}

display ccs::get_config_chain

display ccs::read_mem 2 0x1E60018 4 0 1