======================================================================== 74F245 OCTAL BIDIRECTIONAL TRANSCEIVER (WITH 3-STATE INPUTS/OUTPUTS) ======================================================================== Family: Fairchild FAST (Advanced Schottky TTL) Source: 1985 Fairchild FAST Data Book, pages 4-158 ... 4-159. The 1980 data book carries the 'F245 in its Section 3 selection guide only (page 3-28, description and logic symbol). Status: Released data sheet Ratings: Vcc = +5.0 V +/-5%, TA = 0 to +70 deg C DESCRIPTION ----------- The 'F245 contains eight non-inverting bidirectional buffers with 3-state outputs and is intended for bus-oriented applications. Current sinking capability is 20 mA at the A ports and 64 mA at the B ports. The Transmit/Receive (T//R) input determines the direction of data flow through the bidirectional transceiver. Transmit (active HIGH) enables data from A ports to B ports; Receive (active LOW) enables data from B ports to A ports. The Output Enable input, when HIGH, disables both A and B ports by placing them in a High Z condition. o Non-Inverting Buffers o Bidirectional Data Path o B Outputs Sink 64 mA CONNECTION DIAGRAM (20-pin DIP) ------------------------------- Pin Function Pin Function --- ------------------------ --- ------------------------ 1 T//R Transmit/Receive 20 Vcc 2 A0 Bus A, bit 0 19 /OE Output Enable 3 A1 Bus A, bit 1 18 B0 Bus B, bit 0 4 A2 Bus A, bit 2 17 B1 Bus B, bit 1 5 A3 Bus A, bit 3 16 B2 Bus B, bit 2 6 A4 Bus A, bit 4 15 B3 Bus B, bit 3 7 A5 Bus A, bit 5 14 B4 Bus B, bit 4 8 A6 Bus A, bit 6 13 B5 Bus B, bit 5 9 A7 Bus A, bit 7 12 B6 Bus B, bit 6 10 GND 11 B7 Bus B, bit 7 Each of the eight channels contains a back-to-back pair of non-inverting 3-state buffers; T//R selects which of the pair is enabled, and /OE gates both. TRUTH TABLE ----------- Inputs ------------ /OE T//R Output --- ---- ------------------ L L Bus B Data to Bus A L H Bus A Data to Bus B H X High Z State H = HIGH voltage level; L = LOW voltage level; X = immaterial. INPUT LOADING / FAN-OUT ----------------------- Pin Names Description U.L. HIGH/LOW ---------- ---------------------------------- ------------- /OE Output Enable Input (Active LOW) 0.5 / 0.75 T//R Transmit/Receive Input 0.5 / 0.75 A0 - A7 Side A 3-State Inputs 1.75 / 0.406 3-State Outputs 75 / 15 B0 - B7 Side B 3-State Inputs or 1.75 / 0.406 3-State Outputs 75 / 40 DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE --------------------------------------------------- Symbol Parameter Min Typ Max Units Conditions ------ -------------------- --- --- --- ----- ---------- ICCH Power Supply Current 70 90 mA Vcc = Max ICCL Power Supply Current 95 120 mA Vcc = Max ICCZ Power Supply Current 85 110 mA Vcc = Max AC CHARACTERISTICS ------------------ TA = +25 C 74F Vcc = +5.0V TA/Vcc = Com Symbol Parameter CL Min Typ Max Min Max Units ------ ----------------------------- ----- --- --- --- --- --- ----- tPLH Prop Delay An to Bn or Bn to 50 pF 2.5 4.2 6.0 2.5 7.0 ns An tPHL Prop Delay An to Bn or Bn to 50 pF 2.5 4.6 6.0 2.5 7.0 ns An tPZH Output Enable Time 50 pF 3.0 5.3 7.0 3.0 8.0 ns tPZL Output Enable Time 50 pF 3.5 6.0 8.0 3.5 9.0 ns tPHZ Output Disable Time 50 pF 3.0 5.0 6.5 3.0 7.5 ns tPLZ Output Disable Time 50 pF 2.0 5.0 6.5 2.0 7.5 ns