SN74ACT2228中文资料256 x 1 x 2 双独立同步 FIFO 存储器数据手册TI规格书

描述 Description

The SN74ACT2226 and SN74ACT2228 are dual FIFOs suited for a wide range of serial-data buffering applications, including elastic stores for frequencies up to T2 telecommunication rates. Each FIFO on the chip is arranged as 64 × 1 (SN74ACT2226) or 256 × 1 (SN74ACT2228) and has control signals and status flags for independent operation. Output flags for each FIFO include input ready (1IR or 2IR), output ready (1OR or 2OR), half full (1HF or 2HF), and almost full/almost empty (1AF/AE or 2AF/AE). Serial data is written into a FIFO on the low-to-high transition of the write-clock (1WRTCLK or 2WRTCLK) input when the write-enable (1WRTEN or 2WRTEN) input and input-ready flag (1IR or 2IR) output are both high. Serial data is read from a FIFO on the low-to-high transition of the read-clock (1RDCLK or 2RDCLK) input when the read-enable (1RDEN or 2RDEN) input and output-ready flag (1OR or 2OR) output are both high. The read and write clocks of a FIFO can be asynchronous to one another. Each input-ready flag (1IR or 2IR) is synchronized by two flip-flop stages to its write clock (1WRTCLK or 2WRTCLK), and each output-ready flag (1OR or 2OR) is synchronized by three flip-flop stages to its read clock (1RDCLK or 2RDCLK). This multistage synchronization ensures reliable flag-output states when data is written and read asynchronously. A half-full flag (1HF or 2HF) is high when the number of bits stored in its FIFO is greater than or equal to half the depth of the FIFO. An almost-full/almost-empty flag (1AF/AE or 2AF/AE) is high when eight or fewer bits are stored in its FIFO and when eight or fewer empty locations are left in the FIFO. A bit present on the data output is not stored in the FIFO. The SN74ACT2226 and SN74ACT2228 are characterized for operation from -40°C to 85°C. For more information on this device family, see the application reportFIFOs With a Word Width of One Bit (literature number SCAA006).

特性 Features

• Dual Independent FIFOs Organized as:
• 64 Words by 1 Bit Each - SN74ACT2226
• 256 Words by 1 Bit Each - SN74ACT2228
• Free-Running Read and Write Clocks Can Be Asynchronous or Coincident on Each FIFO
• Input-Ready Flags Synchronized to Write Clocks
• Output-Ready Flags Synchronized to Read Clocks
• Half-Full and Almost-Full/Almost-Empty Flags
• Support Clock Frequencies up to 22 MHz
• Access Times of 20 ns
• Low-Power Advanced CMOS Technology
• Packaged in 24-Pin Small-Outline Integrated-Circuit Package

简介

SN74ACT2228属于集成电路（IC）的FIFO存储器。由TI制造生产的SN74ACT2228FIFO 存储器先入先出 (FIFO) 存储器可用于数字信息的短期存储，其中信息检索顺序和序列与信息存储顺序和序列相同。这类产品又称为队列或缓冲存储器，通常用于在单独的设备之间交换信息，尤其是在数据以不同的速率或在略微不同的时间点生成和使用的情况下。