======================================================================== 74F182 CARRY LOOKAHEAD GENERATOR ======================================================================== Family: Fairchild FAST (Advanced Schottky TTL) Source: 1980 Fairchild FAST Data Book, pages 4-41 ... 4-44 Status: PRELIMINARY -- page 4-41 carries a "Preliminary" watermark. Ratings: Vcc = +5.0 V +/-5%, TA = 0 to +70 deg C DESCRIPTION ----------- The 'F182 is a high speed carry lookahead generator. It is generally used with the 'F181, 'F381 or 2901A 4-bit arithmetic logic unit to provide high speed lookahead over word lengths of more than four bits. o PROVIDES LOOKAHEAD CARRIES ACROSS A GROUP OF FOUR ALU'S o MULTI-LEVEL LOOKAHEAD FOR HIGH SPEED ARTITHMETIC OPERATION OVER LONG WORD LENGTHS FUNCTIONAL DESCRIPTION ---------------------- The 'F182 carry lookahead generator accepts up to four pairs of active LOW Carry Propagate (/P0 - /P3) and Carry Generate (/G0 - /G3) signals and an active HIGH Carry input (Cn) and provides anticipated active HIGH carries (Cn+x, Cn+y, Cn+z) across four groups of binary adders. The 'F182 also has active LOW Carry Propagate (/P) and Carry Generate (/G) outputs which may be used for further levels of lookahead. The logic equations provided at the outputs are: Cn+x = G0 + P0*Cn Cn+y = G1 + P1*G0 + P1*P0*Cn Cn+z = G2 + P2*G1 + P2*P1*G0 + P2*P1*P0*Cn /G = /(G3 + P3*G2 + P3*P2*G1 + P3*P2*P1*G0) /P = /(P3*P2*P1*P0) Also, the 'F182 can be used with binary ALUs in an active LOW or active HIGH input operand mode. The connections to and from the ALU to the carry lookahead generator are identical in both cases. Carries are rippled between lookahead blocks. There are several possible arrangements for the carry interconnects, but all achieve about the same speed. A 28-bit ALU is formed by dropping the last 'F181 or 'F381. CONNECTION DIAGRAM (16-pin DIP) ------------------------------- Pin Function Pin Function --- ----------------------------- --- --------------------------- 1 /G1 Carry Generate input 1 16 Vcc 2 /P1 Carry Propagate input 1 15 /P2 Carry Propagate input 2 3 /G0 Carry Generate input 0 14 /G2 Carry Generate input 2 4 /P0 Carry Propagate input 0 13 Cn Carry input 5 /G3 Carry Generate input 3 12 Cn+x Carry output x 6 /P3 Carry Propagate input 3 11 Cn+y Carry output y 7 /P Carry Propagate output 10 /G Carry Generate output 8 GND 9 Cn+z Carry output z TRUTH TABLE ----------- H = HIGH voltage level; L = LOW voltage level; X = immaterial; blank = not relevant to that output. Cn+x ~~~~ Cn /G0 /P0 Cn+x -- --- --- ---- X H H L L H X L X L X H H X L H Cn+y ~~~~ Cn /G0 /P0 /G1 /P1 Cn+y -- --- --- --- --- ---- X X X H H L X H H H X L L H X H X L X X X L X H X L X X L H H X L X L H Cn+z ~~~~ Cn /G0 /P0 /G1 /P1 /G2 /P2 Cn+z -- --- --- --- --- --- --- ---- X X X X X H H L X X X H H H X L X H H H X H X L L H X H X H X L X X X X X L X H X X X L X X L H X L X X L X L H H X L X L X L H /G ~~ /G0 /G1 /P1 /G2 /P2 /G3 /P3 /G --- --- --- --- --- --- --- --- X X X X X H H H X X X H H H X H X H H H X H X H H H X H X H X H X X X X X L X L X X X L X X L L X L X X L X L L L X L X L X L L /P ~~ /P0 /P1 /P2 /P3 /P --- --- --- --- --- H X X X H X H X X H X X H X H X X X H H L L L L L INPUT LOADING / FAN-OUT ----------------------- Pin Names Description U.L. HIGH/LOW ------------- ----------------------------------- ------------- Cn Carry Input 0.5 / 0.375 /G0, /G2 Carry Generate Inputs (Active LOW) 0.5 / 2.625 /G1 Carry Generate Input (Active LOW) 0.5 / 3.0 /G3 Carry Generate Input (Active LOW) 0.5 / 1.5 /P0, /P1 Carry Propagate Inputs (Active LOW) 0.5 / 1.5 /P2 Carry Propagate Input (Active LOW) 0.5 / 1.125 /P3 Carry Propagate Input (Active LOW) 0.5 / 1.75 Cn+x - Cn+z Carry Outputs 25 / 12.5 /G Carry Generate Output (Active LOW) 25 / 12.5 /P Carry Propagate Output (Active LOW) 25 / 12.5 DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified) -------------------------------------------------------------------------------- Symbol Parameter Min Typ Max Units Cond. ------ --------------------------------------- --- --- --- ----- ----- ICCH Power Supply Current (All Outputs HIGH) 11 mA (1) ICCL Power Supply Current (All Outputs LOW) 19 mA (2) (1) Vcc = Max; /P3, /G3 = 4.5 V; all other inputs = Gnd (2) Vcc = Max; /G0, /G1, /G2 = 4.5 V; all other inputs = Gnd AC CHARACTERISTICS ------------------ Symbol Propagation Delay Path Min Typ Max Units ------ ----------------------------------- --- --- --- ----- tPLH Cn to Cn+x, Cn+y, Cn+z -- 4.6 -- ns tPHL Cn to Cn+x, Cn+y, Cn+z -- 4.5 -- ns tPLH /P0, /P1 or /P2 to Cn+x, Cn+y, Cn+z -- 2.9 -- ns tPHL /P0, /P1 or /P2 to Cn+x, Cn+y, Cn+z -- 2.8 -- ns tPLH /G0, /G1 or /G2 to Cn+x, Cn+y, Cn+z -- 2.9 -- ns tPHL /G0, /G1 or /G2 to Cn+x, Cn+y, Cn+z -- 2.8 -- ns tPLH /P1, /P2 or /P3 to /G -- 4.5 -- ns tPHL /P1, /P2 or /P3 to /G -- 4.3 -- ns tPLH /Gn to /G -- 4.5 -- ns tPHL /Gn to /G -- 4.3 -- ns tPLH /Pn to /P -- 5.0 -- ns tPHL /Pn to /P -- 4.8 -- ns