Our design with the AM3354 (> 30 k in the field) has resistors on the LCD bus to configure SYSBOOT, all works fine.
But recently we got 3 reports of devices not booting (we call them black screens), only solution is to switch power for 30 seconds.
The reset button doesn’t work in this situation, the reset button is connected to /WARMRST, so in this situation SYSBOOT isn’t updated ?
I finely got a failing device on my desk from the field in this state, it was put on battery backup power during transportation.
All voltage where ok and the 26MHz clock was running, reset button didn’t work.
With the JTAG and a XDS200 I could connect to the AM3354 and found SYSBOOT to be 0x00000300 ???
I could also reset (HW and SW) the AM3354 with the JTAG (CC studio) and it was running ROM code but no debug output.
Running the script also confirmed the faulty SYSBOOT value :
CONTROL: device_id = 0x2b94402e
* AM335x family
* Silicon Revision 2.1
PRM_DEVICE: PRM_RSTST = 0x00000021
* Bit 0 : GLOBAL_COLD_RST
* Bit 5 : EXTERNAL_WARM_RST
CONTROL: control_status = 0x00000300
* SYSBOOT[15:14] = 00b (19.2 MHz)
* SYSBOOT[11:10] = 00b No GPMC CS0 addr/data muxing
* Device Type = General Purpose (GP)
* SYSBOOT[7:6] = 00b MII (EMAC boot modes only)
* SYSBOOT[5] = 0 CLKOUT1 disabled
* RESERVED BOOT SEQUENCE!
ROM: Current tracing vector, word 1 = 0x00000006
* Bit 1 : [General] Entered main function
* Bit 2 : [General] Running after the cold reset
ROM: Current tracing vector, word 1 = 0x00000000
ROM: Current tracing vector, word 1 = 0x00000000
ROM: Current copy of PRM_RSTST = 0x00000000
ROM: Cold reset tracing vector, word 1 = 0x00000000
ROM: Cold reset tracing vector, word 1 = 0x00000000
ROM: Cold reset tracing vector, word 1 = 0x00000021
* Bit 0 : [Memory Boot] Memory booting device NULL
* Bit 5 : [Memory Boot] Memory booting device MMCSD0
Cortex A8 Program Counter = 0x00021408 R0 = 0x00000000 R1 = 0x44e00000
Should issuing a HW reset from CC studio on the JTAG not make SYSBOOT be updated ?
Finally I switched off the power for 30 sec and on again, yes all performed well again.
What are the possible reasons for SYSBOOT the be incorrect please ?
Ps : got dump off all registers and SRAM memory.
