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IDT7207L50JB Datasheet(PDF) 8 Page - Integrated Device Technology |
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IDT7207L50JB Datasheet(HTML) 8 Page - Integrated Device Technology |
8 / 12 page 5.05 8 IDT7207 CMOS ASYNCHRONOUS FIFO 32,768 x 9 MILITARY AND COMMERCIAL TEMPERATURE RANGES Figure 11. Expansion In corresponding input control signals of multiple devices. Sta- tus flags ( EF, FF and HF) can be detected from any one device. Figure 13 demonstrates an 18-bit word width by using two IDT7207s. Any word width can be attained by adding addi- tional IDT7207s (Figure 13). Bidirectional Operation Applications which require data buffering between two systems (each system capable of Read and Write operations) can be achieved by pairing IDT7207s as shown in Figure 16. Both Depth Expansion and Width Expansion may be used in this mode. Data Flow-Through Two types of flow-through modes are permitted, a read flow-through and write flow-through mode. For the read flow- through mode (Figure 17), the FIFO permits a reading of a single word after writing one word of data into an empty FIFO. The data is enabled on the bus in (tWEF + tA) ns after the rising edge of W, called the first write edge, and it remains on the bus until the R line is raised from LOW-to-HIGH, after which the bus would go into a three-state mode after tRHZ ns. The EF line would have a pulse showing temporary deassertion and then would be asserted. In the write flow-through mode (Figure 18), the FIFO permits the writing of a single word of data immediately after reading one word of data from a full FIFO. The R line causes the FF to be deasserted but the W line being LOW causes it to be asserted again in anticipation of a new data word. On the rising edge of W, the new word is loaded in the FIFO. The W line must be toggled when FF is not asserted to write new data in the FIFO and to increment the write pointer. Compound Expansion The two expansion techniques described above can be applied together in a straightforward manner to achieve large FIFO arrays (see Figure 15). W R XI WRITE TO FIRST PHYSICAL LOCATION t XIS READ FROM FIRST PHYSICAL LOCATION t XIS t XI t XIR 3140 drw 14 OPERATING MODES: Care must be taken to assure that the appropriate flag is monitored by each system (i.e. FF is monitored on the device where W is used; EF is monitored on the device where R is used). For additional information, refer to Tech Note 8: Oper- ating FIFOs on Full and Empty Boundary Conditions and Tech Note 6: Designing with FIFOs. Single Device Mode A single IDT7207 may be used when the application requirements are for 32,768 words or less. The IDT7207 is in a Single Device Configuration when the Expansion In ( XI) control input is grounded (see Figure 12). Depth Expansion The IDT7207 can easily be adapted to applications when the requirements are for greater than 32,768 words. Figure 14 demonstrates Depth Expansion using three IDT7207s. Any depth can be attained by adding additional IDT7207s. The IDT7207 operates in the Depth Expansion mode when the following conditions are met: 1. The first device must be designated by grounding the First Load ( FL) control input. 2. All other devices must have FL in the HIGH state. 3. The Expansion Out ( XO) pin of each device must be tied to the Expansion In ( XI) pin of the next device. See Figure 14. 4. External logic is needed to generate a composite Full Flag ( FF) and Empty Flag (EF). This requires the ORing of all EFs and ORing of all FFs (i.e. all must be set to generate the correct composite FF or EF). See Figure 14. 5. The Retransmit ( RT) function and Half-Full Flag (HF) are not available in the Depth Expansion Mode. For additional information, refer to Tech Note 9: Cascading FIFOs or FIFO Modules. USAGE MODES: Width Expansion Word width may be increased simply by connecting the |
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