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Altera_Forum
Honored Contributor
17 years agoCyclone3 Power Up level doesn't work
A design with an EP3C40F324I7 has the pin U18 as an registered output. This pin is used to control another dcdc's nSHDN (Shutdown negativ logic) The fpga is configured via epcs. this dcdc is ...
Altera_Forum
Honored Contributor
17 years ago@Daixiwen
The datasheet http://www.altera.com/literature/hb/cyc3/cyc3_ciii52001.pdf says on page 9 table 1-10 pull up min 7k @ 3V page 10 part 2 of 2 for this table pull down min 6k @ 3V so it must be possible as the parameter says "Value of I/O pin pull-down resistor before and during configuration" and thats what i am looking for. enabling this pull down to set this pin to 0 until user mode is entered. but i guess you are right as note 1 for this table says that the pull down feature is only available for JTAG TCK :-( @ Jake i tried different ways //verilog 1995 reg Enable_3V /* synthesis altera_attribute = "-name POWER_UP_LEVEL LOW" */; // Verilog 2001 (* altera_attribute = "-name POWER_UP_LEVEL LOW" *) reg Enable_3V; as well as reg Enable_3V = 1'b0; but none of them works. between power on and until the fpga starts to work in user mode the pin is 1 as soon as the user mode is reached, this pin goes to 0 so it seems that it is realy impossible ... i can't go to 2k pull down as this will disable the soft start function of the dcdc