SN74HC161DR/AIP74HC161_逻辑_框图

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The AiP74HC/HCT161 is a synchronous presettable binary counter with an internal look-head carry. 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 HIGH or LOW. A LOW at the parallel enable input (P¯E¯) 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. Preset takes place regardless of the levels at count enable inputs (CEP and CET).

A LOW at the master reset input (M¯R¯) sets Q0 to Q3 LOW regardless of the levels at input pins CP, P¯E¯, CET and CEP (thus providing an asynchronous clear function). The look-ahead carry simplifies serial cascading of the counters. Both 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 output of Q0.

SN74HC161DR/AIP74HC161_逻辑_框图通讯

This pulse can be used to enable the next cascaded 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)+tSU(CEP to CP))

Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.

其紧张特点如下：

● Input levels:

For AiP74HC161: CMOS level

For AiP74HCT161: TTL level

● Synchronous counting and loading

● 2 count enable inputs for n-bit cascading

● Asynchronous reset

● Positive-edge triggered clock

● Specified from -40℃ to +105℃

● Packaging information: DIP16/SOP16/TSSOP16