SN74LS197N

The purpose of the Master Reset (MR) input in both circuit types of the SN54/74LS196 and SN54/74LS197 counters is to override all other inputs and asynchronously force all outputs LOW. This feature allows for a complete reset of the counters, ensuring that they start from a known state regardless of the previous inputs. The Master Reset input is active LOW, meaning it triggers when a LOW signal is applied to it. This functionality makes the circuits more versatile and usable in various applications.

The SN54/74LS196 and SN54/74LS197 counters have different counting modes available. The SN54/74LS196 can count in BCD (8, 4, 2, 1) sequence or in a bi-quinary mode, producing a 50% duty cycle output. On the other hand, the SN54/74LS197 can be used as a modulo-16 binary counter. Both counters have a Master Reset input that overrides all other inputs and asynchronously forces all outputs LOW. They also have a Parallel Load input that loads data from the Parallel Data inputs into the flip-flops, making them usable as programmable counters. Additionally, the counters can be used as 4-bit latches, loading data when the Parallel Load input is LOW and storing the data when it is HIGH.

The typical power dissipation for the SN54/74LS196 decade counter is 80 mW .