Posted on December 15, 2003 at 14:01Hello,
for our embedded application we use a STPC Atlas configured in ISA mode.
The design is done according to the ST Reference Design Rev. C from 27. Feb. 2002 and Hardware Manual Issue 1.0 from 24.July 2002 (esp. Boot Straps).
Now the problem: the STPC hangs during startup. We checked BIOS-Access with a Logic Analyzer. It gets the first four Bytes from the BIOS and then stops working, though all clocks like HCLK, MCLK, PCICLK are still working correctly.
(HCLK = MCLK = 66 MHz (synchronized), PCICLK = 33MHz and ISACLK = 7.14 MHz). There are also no external events, like interrupts or DMA-Requests.
The measured supply voltages are : V_Core = 2,6V and V_DD = 3,3 V.
We changed Boot-Strap-Resistors from 470k to 100k and 4k7 without effect.
Instead of the BIOS, we put a small test program in to the Flash-PROM. It's just a small endless loop, starting at address 3FFF0h with a jump and some NOPs. We then observed PCI-Control-Signals, like Frame#, IRDY#, TRDY#, DEVSEL#, STOP# and C/BE#. We observed a lot of retrys (DEVSEL# and STOP# are active) but no TRDY# active in order to complete transaction. After it performed several retys it hangs - only clocks are working.
In order to read from Flash-PROM the STPC should use a Memory Read (C/BE# = 6h), but instead it uses a Reserved Command (C/BE# = 4h).
Now, how can it read the first four Bytes of the Flash-PROM using a C/BE# = 4h ??
All C/BE#-Lines are connected correctly (C/BE# = 2h has also been observed).
Please help !
Regards
