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IDT72831L12PF Datasheet(PDF) 6 Page - Integrated Device Technology |
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IDT72831L12PF Datasheet(HTML) 6 Page - Integrated Device Technology |
6 / 21 page 5.15 6 COMMERCIAL TEMPERATURE 72801/72811/72821/72831/72841 DUAL CMOS SyncFIFO ™ 256 x 9, 512 x 9, 1024 x 9, 2048 x 9 and 4096 x 9 Read Clock (RCLKA, RCLKB) — Data can be read from Array A (B) on the the LOW-to-HIGH transition of RCLKA (RCLKB). The Empty Flag EFA (EFB) and Programmable Almost-Empty Flag PAEA (PAEB) are synchronized with re- spect to the LOW-to-HIGH transition of RCLKA (RCLKB). The write and read clock can be asynchronous or coinci- dent. Read Enables ( RENA1 RENA1, RENA2 RENA2, RENB1 RENB1, RENB2 RENB2) — When both Read Enables RENA1, RENA2 (RENB1, RENB2) are LOW, data is read from Array A (B) to the output register on the LOW-to-HIGH transition of the read clock RCLKA (RCLKB). When either of the two Read Enable RENA1, RENA2 ( RENB1, RENB2) associated with FIFO A (B) is HIGH, the output register holds the previous data and no new data is allowed to be loaded into the register. When all the data has been read from FIFO A (B), the Empty Flag EFA (EFB) will go LOW, inhibiting further read operations. Once a valid write operation has been accom- plished, EFA (EFB) will go HIGH after tREF and a valid read can begin. The Read Enables RENA1, RENA2 (RENB1, RENB2) are ignored when FIFO A (B) is empty. Output Enable ( OEA OEA, OEB OEB) — When Output Enable OEA ( OEB) is enabled (LOW), the parallel output buffers of FIFO A (B) receive data from their respective output register. When Output Enable OEA (OEB) is disabled (HIGH), the QA (QB) output data bus is in a high-impedance state. Write Enable 2/Load (WENA2/ LDA LDA, WENB2/LDB LDB) — This is a dual-purpose pin. FIFO A (B) is configured at Reset to have programmable flags or to have two write enables, which allows depth expansion. If WENA2/ LDA (WENB2/LDB) is set HIGH at Reset RSA = LOW (RSB = LOW), this pin operates as a second write enable pin. If FIFO A (B) is configured to have two write enables, when Write Enable 1 WENA1 (WENB1) is LOW and WENA2/LDA (WENB2/ LDB) is HIGH, data can be loaded into the input register and RAM array on the LOW-to-HIGH transition of every write clock WCLKA (WCLKB). Data is stored in the array sequentially and independently of any on-going read operation. In this configuration, when WENA1 (WENB1) is HIGH and/ or WENA2/ LDA (WENB2/LDB) is LOW, the input register of Array A holds the previous data and no new data is allowed to be loaded into the register. To prevent data overflow, the Full Flag FFA (FFB) will go LOW, inhibiting further write operations. Upon the completion of a valid read cycle, FFA (FFB) will go HIGH after tWFF, al- lowing a valid write to begin. WENA1, (WENB1) and WENA2/ LDA (WENB2/LDB) are ignored when the FIFO is full. FIFO A (B) is configured to have programmable flags when the WENA2/ LDA (WENB2/LDB) is set LOW at Reset RSA = LOW ( RSB = LOW). Each FIFO contains four 8-bit offset registers which can be loaded with data on the inputs, or read on the outputs. See Figure 3 for details of the size of the registers and the default values. SIGNAL DESCRIPTIONS FIFO A and FIFO B are identical in every respect. The following description explains the interaction of input and output signals for FIFO A. The corresponding signal names for FIFO B are provided in parentheses. INPUTS: Data In (DA0 – DA8, DB0 – DB8) — DA0 - DA8 are the nine data inputs for memory array A. DB0 - DB8 are the nine data inputs for memory array B. CONTROLS: Reset ( RSA RSA, RSB RSB) — Reset of FIFO A (B) is accomplished whenever RSA (RSB) input is taken to a LOW state. During reset, the internal read and write pointers associated with the FIFO are set to the first location. A reset is required after power-up before a write operation can take place. The Full Flag FFA (FFB) and Programmable Almost-Full Flag PAFA ( PAFB) will be reset to HIGH after tRSF. The Empty Flag EFA ( EFB)andProgrammableAlmost-EmptyFlagPAEA(PAEB)will be reset to LOW after tRSF. During reset, the output register is initialized to all zeros and the offset registers are initialized to their default values. Write Clock (WCLKA, WCLKB) — A write cycle to Array A (B) is initiated on the LOW-to-HIGH transition of WCLKA (WCLKB). Data set-up and hold times must be met with respect to the LOW-to-HIGH transition of WCLKA (WCLKB). The Full Flag FFA (FFB) and Programmable Almost-Full Flag PAFA (PAFB) are synchronized with respect to the LOW-to- HIGH transition of the write clock WCLKA (WCLKB). The write and read clocks can be asynchronous or coinci- dent. Write Enable 1 ( WENA1 WENA1, WENB1 WENB1) — If FIFO A (B) is con- figured for programmable flags, WENA1 (WENB1) is the only enable control pin. In this configuration, when WENA1 (WENB1) is LOW, data can be loaded into the input register of RAM Array A (B) on the LOW-to-HIGH transition of every write clock WCLKA (WCLKB). Data is stored in Array A (B) sequentially and independently of any on-going read operation. In this configuration, when WENA1 (WENB1) is HIGH, the input register holds the previous data and no new data is allowed to be loaded into the register. If the FIFO is configured to have two write enables, which allows for depth expansion. See Write Enable 2 paragraph below for operation in this configuration. To prevent data overflow, FFA (FFB) will go LOW, inhibiting further write operations. Upon the completion of a valid read cycle, the FFA (FFB) will go HIGH after tWFF, allowing a valid write to begin. WENA1 (WENB1) is ignored when FIFO A (B) is full. |
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