SN54AS867
- Fully Programmable With Synchronous Counting and Loading
- SN74ALS867A and ´AS867 Have Asynchronous Clear; SN74ALS869 and ´AS869 Have Synchronous Clear
- Fully Independent Clock Circuit Simplifies Use
- Ripple-Carry Output for n-Bit Cascading
- Package Options Include Plastic Small-Outline (DW) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (NT) and Ceramic (JT) 300-mil DIPs
These synchronous, presettable, 8-bit up/down counters feature internal-carry look-ahead circuitry for cascading in high-speed counting applications. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincidentally with each other when so instructed by the count-enable (,) inputs and internal gating. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters. A buffered clock (CLK) input triggers the eight flip-flops on the rising (positive-going) edge of the clock waveform.
These counters are fully programmable; they may be preset to any number between 0 and 255. The load-input circuitry allows parallel loading of the cascaded counters. Because loading is synchronous, selecting the load mode disables the counter and causes the outputs to agree with the data inputs after the next clock pulse.
The carry look-ahead circuitry provides for cascading counters for n-bit synchronous applications without additional gating. Two count-enable (and ) inputs and a ripple-carry () output are instrumental in accomplishing this function. Both and must be low to count. The direction of the count is determined by the levels of the select (S0, S1) inputs as shown in the function table. is fed forward to enable . thus enabled produces a low-level pulse while the count is zero (all outputs low) counting down or 255 counting up (all outputs high). This low-level overflow-carry pulse can be used to enable successive cascaded stages. Transitions at and are allowed regardless of the level of CLK. All inputs are diode clamped to minimize transmission-line effects, thereby simplifying system design.
These counters feature a fully independent clock circuit. With the exception of the asynchronous clear on the SN74ALS867A and ´AS867, changes at S0 and S1 that modify the operating mode have no effect on the Q outputs until clocking occurs. For the ´AS867 and ´AS869, any time ENP\ and/or ENT\ is taken high, either goes or remains high. For the SN74ALS867A and SN74ALS869, any time is taken high, either goes or remains high. The function of the counter (whether enabled, disabled, loading, or counting) is dictated solely by the conditions meeting the stable setup and hold times.
The SN54AS867 and SN54AS869 are characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ALS867A, SN74ALS869, SN74AS867, and SN74AS869 are characterized for operation from 0°C to 70°C.
技术文档
类型 | 标题 | 下载最新的英语版本 | 日期 | |||
---|---|---|---|---|---|---|
* | 数据表 | Synchronous 8-Bit Up/Down Counters 数据表 (Rev. C) | 1995年 1月 1日 | |||
* | SMD | SN54AS867 SMD 5962-89668 | 2016年 6月 21日 | |||
选择指南 | Logic Guide (Rev. AB) | 2017年 6月 12日 | ||||
应用手册 | Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) | 2015年 12月 2日 | ||||
选择指南 | 逻辑器件指南 2014 (Rev. AA) | 最新英语版本 (Rev.AB) | 2014年 11月 17日 | |||
用户指南 | LOGIC Pocket Data Book (Rev. B) | 2007年 1月 16日 | ||||
应用手册 | Semiconductor Packing Material Electrostatic Discharge (ESD) Protection | 2004年 7月 8日 | ||||
应用手册 | TI IBIS File Creation, Validation, and Distribution Processes | 2002年 8月 29日 | ||||
应用手册 | 使用逻辑器件进行设计 (Rev. C) | 1997年 6月 1日 | ||||
应用手册 | Advanced Schottky Load Management | 1997年 2月 1日 | ||||
应用手册 | Input and Output Characteristics of Digital Integrated Circuits | 1996年 10月 1日 | ||||
应用手册 | Live Insertion | 1996年 10月 1日 | ||||
应用手册 | Advanced Schottky (ALS and AS) Logic Families | 1995年 8月 1日 |
设计和开发
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封装 | 引脚 | CAD 符号、封装和 3D 模型 |
---|---|---|
CDIP (JT) | 24 | Ultra Librarian |
订购和质量
- RoHS
- REACH
- 器件标识
- 引脚镀层/焊球材料
- MSL 等级/回流焊峰值温度
- MTBF/时基故障估算
- 材料成分
- 鉴定摘要
- 持续可靠性监测
- 制造厂地点
- 封装厂地点