View sn74gtl16616dggr datasheet:

SN74GTL16616DGGR (1/2) IL08 C-MOS 17-BIT GTL/LVT UNIVERSAL BUS TRANSCEIVERS WITH BUFFERED CLOCK OUTPUTS —TOP VIEW— INPUT CEAB : CLOCK ENABLE (A-TO-B DATA FLOW) 1 56 CEBA : CLOCK ENABLE (B-TO-A DATA FLOW) 2 55 CLKAB : CLOCK (A-TO-B DATA FLOW) 3 54 CLKBA : CLOCK (B-TO-A DATA FLOW) 4 GND GND 53 CLKIN : CLOCK IN 5 52 LEAB : LATCH ENABLE (A-TO-B DATA FLOW) 6 51 LEBA : LATCH ENABLE (B-TO-A DATA FLOW) 7 VDD VDD 50 OEAB : OUTPUT ENABLE (A-TO-B DATA FLOW) 8 49 OEBA : OUTPUT ENABLE (B-TO-A DATA FLOW) 9 48 10 47 OUTPUT 11 GND GND 46 CLKOUT : CLOCK OUT 12 45 13 44 INPUT/OUTPUT 14 43 A1 - A18 : A-BUS DATA 15 42 B1 - B18 : B-BUS DATA 16 41 17 40 18 GND GND 39 INPUTS OUTPUT 19 38 LEAB CLKAB A B CEAB OEAB 20 37 x 1 x x x HI