The GX3501 is an 80 channel, TTL buffer expansion card designed specifically for the GX3500 FLexDIO FPGA card. Each group of 40 channels can be configured with an on-board jumper to support TTL of LVTTL logic levels. Each channel can be configured to an input or output under software control. The GX3501 is also available be ordered as a pre-assembled unit with the GX3500 as part number GX3601.