# Constraints for reference design 's3esk_startup'.
#
# Revision C of the Spartan-3E Starter Kit.
#
# Ken Chapman - Xilinx Ltd - January 2006
#                          
# Revised 16th February 2006
#
# Period constraint for 50MHz operation
#
NET "clk" PERIOD = 20.0ns HIGH 50%;
#
# soldered 50MHz Clock.
# 
NET "clk" LOC = "C9" | IOSTANDARD = LVTTL;
#
#
# Simple LEDs 
# Require only 3.5mA. 
#
NET "led<0>" LOC = "F12" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 4;
NET "led<1>" LOC = "E12" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 4;
NET "led<2>" LOC = "E11" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 4;
NET "led<3>" LOC = "F11" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 4;
NET "led<4>" LOC = "C11" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 4;
NET "led<5>" LOC = "D11" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 4;
NET "led<6>" LOC = "E9"  | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 4;
NET "led<7>" LOC = "F9"  | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 4;
#
#
# LCD display
# Very slow so can use lowest drive strength. 
#
NET "lcd_rs"   LOC = "L18" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
NET "lcd_rw"   LOC = "L17" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
NET "lcd_e"    LOC = "M18" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
NET "lcd_d<4>" LOC = "R15" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
NET "lcd_d<5>" LOC = "R16" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
NET "lcd_d<6>" LOC = "P17" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
NET "lcd_d<7>" LOC = "M15" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
#
# Strata Flash (need to disable to use LCD display) 
#
NET "strataflash_oe" LOC = "C18" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
NET "strataflash_ce" LOC = "D16" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
NET "strataflash_we" LOC = "D17" | IOSTANDARD = LVTTL | SLEW = SLOW | DRIVE = 2;
#
#
# Simple switches 
#   Pull UP resistors used to stop floating condition during switching. 
#
NET "switch<0>" LOC = "L13" | IOSTANDARD = LVTTL | PULLUP;
NET "switch<1>" LOC = "L14" | IOSTANDARD = LVTTL | PULLUP;
NET "switch<2>" LOC = "H18" | IOSTANDARD = LVTTL | PULLUP;
NET "switch<3>" LOC = "N17" | IOSTANDARD = LVTTL | PULLUP;
#
#
# Press buttons 
#   Must have pull DOWN resistors to provide Low when not pressed.
#
NET "btn_north" LOC = "V4"  | IOSTANDARD = LVTTL | PULLDOWN;
NET "btn_east"  LOC = "H13" | IOSTANDARD = LVTTL | PULLDOWN;
NET "btn_south" LOC = "K17" | IOSTANDARD = LVTTL | PULLDOWN;
NET "btn_west"  LOC = "D18" | IOSTANDARD = LVTTL | PULLDOWN;
#
# Rotary encoder. 
#   Rotation contacts require pull UP resistors to provide High level.
#   Press contact requires pull DOWN resistor to provide Low when not pressed..
#
NET "rotary_a"     LOC = "K18" | IOSTANDARD = LVTTL | PULLUP;
NET "rotary_b"     LOC = "G18" | IOSTANDARD = LVTTL | PULLUP;
NET "rotary_press" LOC = "V16" | IOSTANDARD = LVTTL | PULLDOWN;
#
#
# End of File
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