Sir,We develope a board with a hardware watchdog connect to NET+ARM50 's reset pin. But sometime it could not boot up,the Network link led “on” for a while then “off”.so hardware watchdog send reset signal again and again. Does this is NET+ARM50’s problem? Where should I do for this problem? Regards,
To the best of my knowledge, the board designers and end users that plan to use NET+40-4 and NET+50-1 have to avoid the watchdog timer problem. To have a watchdog timer work reliably the design must either: a. Use an external oscillator (PLL disabled). Here you need an SDRAM work-a-round which requires 7 gates (OR, 2 ANDs, EXOR, and 3 NANDs). b. Use an EXTERNAL Watchdog IC (PLL enabled). Here you need an SDRAM work-a-round which requires 3 gates (OR and 2 ANDs). These work-a-rounds are the described briefly in the NET+50 errata posted on the web. Bottom line is that the 50-1 will require an external oscillator or an external watchdog IC for the watch dog RESET timer to work reliably, The 50-3 has corrected this.