Multi-channel FIFO support is slightly different than previous generations of FTDI devices. In previous devices such as the FT4232HL (768-1026-2-ND) the four channels were physically mapped out to individual pins, as shown on the block on the left on this slide. To keep the pin count down with the FT60x series (the blocks on the right) the four channels are functionally defined and share the same set of pins.