NTE Electronics NTE74LS161A

NTE74LS160A through NTE74LS163A are synchronous, presettable counters in 16-pin DIP packages, featuring internal carry look-ahead for high-speed counting designs. NTE74LS160A and NTE74LS162A are decade counters, while NTE74LS161A and NTE74LS163A are 4-bit binary counters. Synchronous operation is achieved by clocking all flip-flops simultaneously, causing outputs to change at the same time under the control of the count enable inputs and internal gating. This mode of operation eliminates the output count spikes typically associated with asynchronous (ripple clock) counters, although count spikes may still appear on the ripple carry output (RCO). The buffered clock input triggers all four flip-flops on the rising edge of the clock input waveform.

These counters are fully programmable — outputs can be preset to any level. Since presetting is synchronous, a LOW on the load input disables the counter and causes the outputs to agree with the setup data after the next clock pulse, regardless of the levels of the enable inputs. The clear function of NTE74LS160A and NTE74LS161A is asynchronous; a LOW on the clear input forces all four flip-flop outputs LOW regardless of the levels of the clock, load, or enable inputs. The clear function of NTE74LS162A and NTE74LS163A is synchronous; a LOW on the clear input forces all four flip-flop outputs LOW after the next clock pulse, regardless of the levels of the enable inputs. This synchronous clear function allows easy modification of the count length, as a single external NAND gate can be used to decode the desired maximum count. The gate output is connected to the clear input to synchronously clear the counter to 0000 (LLLL).

The carry look-ahead circuitry allows cascading of counters for n-bit synchronous applications without additional gating. This is accomplished through two count enable inputs and a ripple carry output. Both count enable inputs (P and T) must be HIGH to count, and input T is fed forward to enable the ripple carry output. When enabled, the ripple carry output produces a HIGH output pulse with a duration approximately equal to the HIGH portion of the QA output. This HIGH overflow ripple carry pulse can be used to enable successive cascaded stages. Transitions on the enable P or T inputs of NTE74LS160A through NTE74LS163A are allowed at any level of the clock input.

NTE74LS160A through NTE74LS163A feature fully independent clock circuitry. Changes on the control inputs (enable P or T, or load) do not affect the mode of operation until the clock is triggered. The counter function (whether enabled, disabled, loaded, or counting) is determined solely by conditions that satisfy the required setup and hold times.

• 4 types available:
• Decade counter with direct clear: NTE74LS160A
• Binary counter with direct clear: NTE74LS161A
• Decade counter with synchronous clear: NTE74LS162A
• Binary counter with synchronous clear: NTE74LS163A
• Internal look-ahead for fast counting
• Carry output for n-bit cascading
• Synchronous counting
• Synchronous programmable
• Load control line
• Diode-clamped inputs