The '190, 'LS190, '191, and 'LS191 are synchronous, reversible up/down counters having a complexity of 58 equivalent gates. The '191 and 'LS191 are 4-bit binary counters and the '190 and 'LS190 are BCD counters. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when so instructed by the steering logic. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple clock) counters.

The outputs of the four master-slave flip-flops are triggered on a low-to-high transition of the clock input if the enable input is low. A high at the enable input inhibits counting. Level changes at the enable input should be made only when the clock input is high. The direction of the count is determined by the level of the down/up input. When low, the counter count up and when high, it counts down. A false clock may occur if the down/up input changes while the clock is low. A false ripple carry may occur if both the clock and enable are low and the down/up input is high during a load pulse.

These counters are fully programmable; that is, the outputs may be preset to either level by placing a low on the load input and entering the desired data at the data inputs. The output will change to agree with the data inputs independently of the level of the clock input. This feature allows the counters to be used as modulo-N dividers by simply modifying the count length with the preset inputs.

The clock, down/up, and load inputs are buffered to lower the drive requirement which significantly reduces the number of clock drivers, etc., required for long parallel words.

Two outputs have been made available to perform the cascading function: ripple clock and maximum/minimum count. The latter output produces a high-level output pulse with a duration approximately equal to one complete cycle of the clock when the counter overflows or underflows. The ripple clock output produces a low-level output pulse equal in width to the low-level portion of the clock input when an overflow or underflow condition exists. The counters can be easily cascaded by feeding the ripple clock output to the enable input of the succeeding counter if parallel clocking is used, or to the clock input if parallel enabling is used. The maximum/minimum count output can be used to accomplish look-ahead for high-speed operation.

Series 54' and 54LS' are characterized for operation over the full military temperature range of -55°C to 125°C; Series 74' and 74LS' are characterized for operation from 0°C to 70°C.

• Counts 8-4-2-1 BCD or Binary
• Single Down/Up Count Control Line
• Count Enable Control Input
• Ripple Clock Output for Cascading
• Asynchronously Presettable with Load Control
• Parallel Outputs
• Cascadable for n-Bit Applications

• TMP122 - 具有 SPI 接口的 ±1°C 温度传感器，支持报警功能，采用 SOT 封装
• UC1901-SP - 隔离反馈生成器
• TAS2505 - 具有音频处理功能和单声道耳机放大器的数字输入 D 类扬声器放大器
• SN54HC02 - 四路 2 输入正与非门
• LMZ36002 - LMZ36002 4.5V 至 60V 输入、2A、SIMPLE SWITCHER 电源模块
• ADC10664 - 具有输入多路复用器和采样/保持功能的 10 位 360 ns A/D 转换器
• UC39431 - 精确可调节的并联稳压器
• TLV5535 - 8 位单通道低功耗 35MSPS ADC
• LM3490 - 具有逻辑控制开/关的 100 mA、SOT-23、准低压降线性稳压器
• TPS54380-Q1 - 用于进行定序的汽车类低输入电压 3A 同步降压转换器