I've got my boards fab. The board design is based on Stamp reference design. I didnt stuff the whole BOM, instead i am taking it step by step.
I have stuffed
-bf537 dsp ,
-25Mhz crystal with its capacitors and resistors,
-the Rtc with caps and res.
-1.2v switching mosfet with required circuitry.
-Pulled Up NMI
-pulled up reset (have not stuffed reset supervisory ic yet)
-jtag (with required pull ups )
when i power up the board, i can see the pwm on the VROUT pin and can measure 1.2 ~ 1.3 v at VDDINT pin.
-The CLKBUF shows 25Mhz (buffered version of the crystal )
-CLKOUT pin shows nothing, and remains low .
-JTAG does not detect the chip (TDO stuck at high error) (i am using urjtag and wiggler for debugging)
my questions is :
-shouldnt CLKOUT always show some clock on power up ? like CLKBUF , because according to itnernal clock circuitry the CLKBUF and CLKOUT are buffered versions of CLKIN and always on .
-what is JTAG detection of chip dependent on ? jtag is fine as i'v tested it on my other working board. (previous version)-
-should JTAG detect teh chip if we power up the system with no extra periperals but the crystal and the 1.2v circuitry ?
The most likely reason that you're not getting CLKOUT and not able to connect over JTAG is that you are not meeting the power-up reset requirements of the BF537. RESET must be held low for at at 3500 CLKIN cycles after all voltage supplies are up. This spec is detailed in table 23 on page 31 of the ADSP-BF534/ADSP-BF536/ADSP-BF537: Blackfin Embedded Processor Data Sheet (Rev I, 07/2010).
solved.. the reset transition was not proper.