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SN74LS293N Datasheet(PDF) 3 Page - Motorola, Inc |
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SN74LS293N Datasheet(HTML) 3 Page - Motorola, Inc |
3 / 7 page 5-468 FAST AND LS TTL DATA SN54/74LS290 D SN54/74LS293 FUNCTIONAL DESCRIPTION The LS290 and LS293 are 4-bit ripple type Decade, and 4-Bit Binary counters respectively. Each device consists of four master / slave flip-flops which are internally connected to provide a divide-by-two section and a divide-by-five (LS290) or divide-by-eight (LS293) section. Each section has a separate clock input which initiates state changes of the counter on the HIGH-to-LOW clock transition. State changes of the Q outputs do not occur simultaneously because of internal ripple delays. Therefore, decoded output signals are subject to decoding spikes and should not be used for clocks or strobes. The Q0 output of each device is designed and specified to drive the rated fan-out plus the CP1 input of the device. A gated AND asynchronous Master Reset (MR1 ⋅ MR2) is provided on both counters which overrides the clocks and resets (clears) all the flip-flops. A gated AND asynchronous Master Set (MS1 ⋅ MS2) is provided on the LS290 which overrides the clocks and the MR inputs and sets the outputs to nine (HLLH). Since the output from the divide-by-two section is not internally connected to the succeeding stages, the devices may be operated in various counting modes: LS290 A. BCD Decade (8421) Counter — the CP1 input must be externally connected to the Q0 output. The CP0 input receives the incoming count and a BCD count sequence is produced. B. Symmetrical Bi-quinary Divide-By-Ten Counter — The Q3 output must be externally connected to the CP0 input. The input count is then applied to the CP1 input and a divide-by-ten square wave is obtained at output Q0. C. Divide-By-Two and Divide-By-Five Counter — No external interconnections are required. The first flip-flop is used as a binary element for the divide-by-two function (CP0 as the input and Q0 as the output). The CP1 input is used to obtain binary divide-by-five operation at the Q3 output. LS293 A. 4-Bit Ripple Counter — The output Q0 must be externally connected to input CP1. The input count pulses are applied to input CP0. Simultaneous division of 2, 4, 8, and 16 are performed at the Q0, Q1, Q2, and Q3 outputs as shown in the truth table. B. 3-Bit Ripple Counter — The input count pulses are applied to input CP1. Simultaneous frequency divisions of 2, 4, and 8 are available at the Q1, Q2, and Q3 outputs. Independent use of the first flip-flop is available if the reset function coincides with reset of the 3-bit ripple-through counter. LS290 MODE SELECTION RESET/SET INPUTS OUTPUTS MR1 MR2 MS1 MS2 Q0 Q1 Q2 Q3 H H L X L L L L H H X L L L L L X X H H H L L H L X L X Count X L X L Count L X X L Count X L L X Count LS290 BCD COUNT SEQUENCE COUNT OUTPUT COUNT Q0 Q1 Q2 Q3 0 L L L L 1 H L L L 2 L H L L 3 H H L L 4 L L H L 5 H L H L 6 L H H L 7 H H H L 8 L L L H 9 H L L H NOTE: Output Q0 is connected to Input CP1 for BCD count. H = HIGH Voltage Level L = LOW Voltage Level X = Don’t Care LS293 MODE SELECTION RESET INPUTS OUTPUTS MR1 MR2 Q0 Q1 Q2 Q3 H H L L L L L H Count H L Count L L Count TRUTH TABLE COUNT OUTPUT COUNT Q0 Q1 Q2 Q3 0 L L L L 1 H L L L 2 L H L L 3 H H L L 4 L L H L 5 H L H L 6 L H H L 7 H H H L 8 L L L H 9 H L L H 10 L H L H 11 H H L H 12 L L H H 13 H L H H 14 L H H H 15 H H H H Note: Output Q0 connected to input CP1. |
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