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Hello,

We produced 8 prototype boards mounting the TI AM3359ZCZ microprocessor.

The selected boot sequence via the SYSBOOT[4..0] pins is b11000: SPI – MMC – USB – UART.

In the lab, we verified that 5 boards boot through SD Card without any problem.

The other 3 boards do not boot (at least via SD Card). The Power Supply Voltages and Current Consumption are at the nominal level and the clock is correct at 26MHz. We cannot debug the device using the JTAG port because we embedded it due to security reasons.

 We cannot see any apparent reason because the boot phase is interrupted.

In the upper picture, there is a scope screenshot representing SD-Card interface signals of 2 booting boards in parallel immediately after the power-up phase.

The traces represent the following signals:

0 – BOARD1 SD_CLK

1 – BOARD1 SD_CMD

2 – BOARD1 SD_DAT3

3 – BOARD1 SD_DAT2

4 – BOARD1 SD_DAT1

5 – BOARD1 SD_DAT0

6 – BOARD2 SD_CLK

7 – BOARD2 SD_CMD

8 – BOARD2 SD_DAT3

9 – BOARD2 SD_DAT2

10 – BOARD2 SD_DAT1

11 – BOARD2 SD_DAT0

BOARD1 (upper traces) boots correctly: it starts with a 125 kHz clock, after a while the clocks switch to 6 MHz and later all 4 data lines are used

BOARD2 (lower traces) stops the boot: the 125 kHz phase is much longer than BOARD1, nevertheless the clock switches to 6 MHz (see the trace number 6 in the following picture).

 BOARD2 seems to stop the SD-Card booting phase.

On the analog scope all the signals seems to be quite clean without overshoot or undershoot, crosstalk and so on.

BOARD2 gives a stream of ‘C’ characters on the terminal window, the stream interrupts cyclically because the device jumps through the boot sequence.

We noted that all the 5 working BOARDS mount an XAM3359ZCZ marked 22AG4IW, the other 3 BOARDS mount an XAM3359ZCZ marked IBA0L3W.

 Thanks in advance for the help!