74LV161

NOTES:
1. Stresses beyond those listed may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
2. The input and output voltage ratings may be exceeded if the input and output current ratings are observed

The 74LV161 is a low-voltage Si-gate CMOS device and is pin and function compatible with 74HC/HCT161.

The 74LV161 is a synchronous presettable binary counter which fatures an internal look-head carry and can be used for high-speed counting. Synchronous operation is provided by having all flip-flops clocked simultaneously on the positive-going edge of the clock (CP).

The outputs (Q₀ to Q₃) of the counters may be preset to a HIGH or LOW level. A LOW level at the parallel enable input (PE) disables the counting action and causes the data at the data inputs (D0 to D3) to be loaded into the counter on the positive-going edge of the clock (providing that the set-up and hold time requirements for PE are met).
Preset takes place regardless of the levels at count enable inputs(CEP and CET). A low level at the master reset input (MR) sets all four outputs of the flip-flops (Q₀ to Q₃) to LOW level regardless of the levels at CP, PE, CET and CEP inputs (thus providing an asynchronous clear function).

The look-ahead carry simplifies serial cascading of the counters.Both count enable inputs (CEP and CET) must be HIGH to count. The CET input is fed forward to enable the terminal count output (TC). The TC output thus enabled will produce a HIGH output pulse of a duration approximately equal to a HIGH level output of Q₀. This pulse of the 74LV161 can be used to enable the next cascading stage. The maximum clock frequency for the cascaded counters is determined by the CP to TC propagation delay and CEP to CP set-up time, according to the following formula:
fmax =1/tp_(max) (CP to TC)+t_su(CEP to CP)