While the first counter counts from 0 to 9, the second counter starts its counting operation every time the count value of first counter reaches 9. This is done by using a 555 Timer IC connected in astable mode to produce the clock pulses of 1 second interval each. The idea is to display clock pulses count from 0 to 59, representing a 60 second time interval. The SN54246/SN74246 and '247 and the SN54LS247/SN74LS247 and 'LS248 compose the 6 and the 9 with tails and were designed to offer the designer a choice between two indicator fonts.This circuit is based on the principle of 2 stage counter operation, based on synchronous cascading. Inputs and outputs are entirely compatible for use with TTL logic outputs. All types (including the '49 and 'LS49) contain an overriding blanking input (BI\), which can be used to control the lamp intensity by pulsing or to inhibit the outputs. Lamp test (LT\) of these types may be performed at any time when the BI\/RBO\ node is at a high level. The '46A, '47A, '48, 'LS47, and 'LS48 circuits incorporate automatic leading and/or trailing-edge zero-blanking control (RBI\ and RBO\). Display patterns for BCD input counts above 9 are unique symbols to authenticate input conditions. Segment identification and resultant displays are shown below. The 'LS49 circuit incorporates a direct blanking input. All of the circuits except 'LS49 have full ripple-blanking input/output controls and a lamp test input. The '48, 'LS48, and 'LS49 feature active-high outputs for driving lamp buffers or common-cathode LEDs. The '46A, '47A, and 'LS47 feature active-low outputs designed for driving, common-anode LEDs or incandescent indicators directly. All Circuit Types Feature Lamp Intensity Modulation Capability.Internal Pull-Ups Eliminate Need for External Resistors.Open-Collector Outputs Drive Indicators Directly.parametric-filter Programmable logic circuits.parametric-filter Monostable multivibrators (one-shots).parametric-filter Digital multiplexers & encoders.parametric-filter Digital demultiplexers & decoders.parametric-filter Digital arithmetic ICs.parametric-filter Bus-termination arrays.parametric-filter Voltage translators & level shifters.parametric-filter Flip-flops, latches & registers.parametric-filter Buffers, drivers & transceiver.parametric-filter Wireless connectivity.parametric-filter Switches & multiplexers.parametric-filter Microcontrollers (MCUs) & processors.parametric-filter Logic & voltage translation.
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