SN54/74LS348 SN54/74LS848 8-INPUT PRIORITY ENCODERS WITH 3-STATE OUTPUTS The SN54 / 74LS348 and the SN54 / 74LS848 are eight input priority encoders which provide the 8-line to 3-line function. The outputs (A0 - A2) and inputs (0 - 7) are active low. The active low input which has the highest priority (input 7 has the highest) is represented on the outputs (output A0 is the lowest bit). An example would be if inputs 1, 2 and 4 were low, then a binary 4 would be represented on the outputs. The GS (Group Signal) output is active low when any of the inputs are low. It serves to indicate when any of the inputs are active. A0, A1 and A2 are three-state outputs. This allows for up to 64 line expansion without the need for special external circuitry. A logical one on the Enable Input (EI) forces A0, A1 ared A2 to the disabled state and outputs GS and EO to the high state. A high on all data inputs (0 - 7) together with a low on the EI input disables outputs A0, A1, and A2 and forces output GS to the high state and output EO to the low state. Use of the EI input in conjunction with the EO output provides for the capability of having priority encoding of n input signals. The LS848 has special internal circuitry providing for a greatly reduced negative going glitch on the GS (Group Signal) output and on a reduced tendency for the A0, A1 and A2 outputs to become momentarily enabled. Both of these occurrences happen when the EI input goes from a logical one to a logical zero and all data inputs (0 - 7) are held at logical ones. The internal glitch reduction circuitry does add an additional fan-in of one on all data inputs (compared to that of the LS348). OUTPUTS VCC 16 INPUTS EO GS 3 2 1 0 OUTPUT A0 15 14 13 12 11 10 9 EO GS 3 2 1 0 4 1 4 8-INPUT PRIORITY ENCODERS WITH 3-STATE OUTPUTS LOW POWER SCHOTTKY J SUFFIX CERAMIC CASE 620-09 16 1 16 1 16 1 6 7 EI A2 A1 2 5 3 6 4 7 5 EI 6 A2 7 A1 INPUTS D SUFFIX SOIC CASE 751B-03 ORDERING INFORMATION A0 5 N SUFFIX PLASTIC CASE 648-08 SN54LSXXXJ SN74LSXXXN SN74LSXXXD 8 GND OUTPUTS FUNCTION TABLE INPUTS OUTPUTS EI 0 1 2 3 4 5 6 7 A2 A1 A0 GS EO H L L L L L L L L L X H X X X X X X X L X H X X X X X X L H X H X X X X X L H H X H X X X X L H H H X H X X X L H H H H X H X X L H H H H H X H X L H H H H H H X H L H H H H H H H Z Z L L L L H H H H Z Z L L H H L L H H Z Z L H L H L H L H H H L L L L L L L L H L H H H H H H H H FAST AND LS TTL DATA 5-1 H = HIGH Logic Level L = LOW Logic Level X = Irrelevant Z = High Impedance State Ceramic Plastic SOIC SN54/74LS348 * SN54/74LS848 BLOCK DIAGRAMS (5) EI (10) 0 (5) EI (10) 0 1 2 3 (15) EO (14)GS (11) G1 G13 G29 1 G31 (11) G2 (12) G3 (13) G4 (1) G5 G10 (2) G6 G11 (3) G7 G12 (4) G8 (15) EO (14) GS G30 G14 (12) (9) A0 2 G9 (13) 4 5 3 (1) (7) A1 (2) 4 7 G16 G18 G17 G19 (7) A1 G20 5 6 (9) A0 G15 G21 (3) G23 G22 6 (4) (6) A2 G24 7 (6) A2 G25 G26 G28 G27 SN54 / 74LS348 SN54 / 74LS848 GUARANTEED OPERATING RANGES Min Typ Max Unit VCC Symbol Supply Voltage Parameter 54 74 4.5 4.75 5.0 5.0 5.5 5.25 V TA Operating Ambient Temperature Range 54 74 - 55 0 25 25 125 70 C IOH Output Current -- High EO, GS 54, 74 - 0.4 mA IOH Output Current -- High A0, A1, A2 A0, A1, A2 54 74 - 1.0 - 2.6 mA IOL Output Current -- Low EO, GS 54 74 4.0 8.0 mA IOL Output Current -- Low A0, A1, A2 A0, A1, A2 54 74 12 24 mA FAST AND LS TTL DATA 5-2 SN54/74LS348 * SN54/74LS848 DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified) Limits S b l Symbol VIH Input HIGH Voltage VIL Input LOW Voltage VIK Input Clamp Diode Voltage Output HIGH Voltage A0, A1, A2 VOH Min P Parameter Typ Max U i Unit 2.0 54 0.7 74 0.8 - 0.65 - 1.5 T Test C Conditions di i V Guaranteed Input HIGH Voltage for All Inputs V Guaranteed Input p LOW Voltage g for All Inputs V VCC = MIN, IIN = - 18 mA 54, 74 2.4 3.1 V EO, GS 54 2.5 3.5 V EO, GS 74 2.7 3.5 V VCC = MIN, IOH = MAX, VIN = VIH or VIL per Truth Table VCC = VCC MIN, VIN = VIL or VIH per Truth Table Output p LOW Voltage g EO, GS 54, 74 0.25 0.4 V VOL IOL = 4.0 mA 74 0.35 0.5 V IOL = 8.0 mA Output p LOW Voltage g A0, A1, A2 54, 74 0.25 0.4 V VOL IOL = 12 mA 74 0.35 0.5 V IOL = 24 mA IOZH Output Off Current HIGH 20 A VCC = MAX, VOUT = 2.7 V IOZL Output Off Current LOW -20 A VCC = MAX, VOUT = 0.4 V Input HIGH Current Input 0, EI -- LS348 20 A Input 0 -- LS848 40 A Other -- LS348 Other -- LS848 40 60 A A Input HIGH Current Input 0, EI -- LS348 0.1 mA Input 0 -- LS848 0.2 mA Other -- LS348 Other -- LS848 0.2 0.3 mA mA Input LOW Current Input 0, EI -- LS348 - 0.4 mA Input 0 -- LS848 - 0.8 mA Other -- LS348 Other -- LS848 - 0.8 - 1.2 mA mA - 20 - 120 mA - 30 - 130 mA IIH IIL IOS Short Circuit Current (Note 1) EO,, GS A0, A1, A2 Power Supply Current Total, Output HIGH 12 23 Total, Output LOW 13 25 ICC VCC = VCC MIN, VIN = VIL or VIH per Truth Table VCC = MAX MAX, VIN = 2.7 27V VCC = MAX MAX, VIN = 7.0 70V VCC = MAX MAX, VIN = 0.4 04V VCC = MAX VCC = MAX All Inputs and Outputs Open mA Note 1: Not more than one output should be shorted at a time, nor for more than 1 second. FAST AND LS TTL DATA 5-3 VCC = MAX, Inputs 7, EI = GND All Others Open SN54/74LS348 * SN54/74LS848 AC CHARACTERISTICS (VCC = 5.0 V, TA = 25C) From (Input) To (Output) 1 thru 7 A0 A1 or A2 A0, LS348 Limits Typ Max 17 12 18 30 20 30 23 35 23 35 23 35 23 35 25 39 25 39 24 41 24 41 Out-of-Phase 11 18 11 18 output 26 40 26 40 In-Phase 38 55 38 55 tPHL output 9.0 21 9.0 21 tPLH In-Phase 11 17 11 17 output 14 36 14 36 In-Phase 17 21 17 21 output 25 40 30 45 18 27 18 27 23 35 23 35 Symbol S b l tPLH tPHL tPLH 1 thru 7 EI Max In-Phase 11 output 20 Out-of-Phase output ns A0 A1 or A2 A0, 0 thru 7 tPLH 0 thru 7 EI tPLH EI tPHZ EI ns GS CL = 15 p pF F RL = 2.0 ns EO tPHL CL = 45 p pF F RL = 667 ns GS tPHL Test Conditions T C di i ns E0 tPHL Unit U i ns tPZL tPLH Min A0 A1 or A2 A0, tPHL tPZH Typ Waveform W f Min LS848 Limits ns A0 A1 or A2 A0, ns tPLZ FAST AND LS TTL DATA 5-4 CL = 5.0 p pF RL = 667