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FPGA: Input/Output pin levels on various family of devices.
XC3000(L), XC4000(E/L/EX/XL), XC5200(L)
Are the I/O pins CMOS or TTL?
Following are the I/O pin levels for Xilinx FPGA devices.
These apply to all the user I/O pins as well as dedicated pins.
Family Inputs Outputs
XC3100A selectable always CMOS
XC3100L CMOS=TTL CMOS=TTL
XC4000E selectable selectable
XC4000L CMOS=TTL CMOS=TTL
XC4000EX selectable selectable
XC4000XL CMOS=TTL CMOS=TTL
XC5200 selectable CMOS
XC5200L CMOS=TTL CMOS=TTL
For 5-V devices, selectable means the user can globally
configure for either TTL or CMOS input thresholds or output levels using Makebits options. The two global selections of input threshold and output levels are independent of each other .
For 3.3-V devices, CMOS=TTL input thresholds mean that the
input threshold is at 50% of Vcc, typical for CMOS, but this voltage is also very close to the traditional TTL input threshold of 1.3 to 1.4 V.
For 3.3-V devices, CMOS=TTL output levels mean that the outputs pull all the way to the positive rail, typical of CMOS, but this voltage is also very close to a traditional TTL output level 0f 3.5 V.