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PEEL18LV8ZSI-15L Datasheet(PDF) 3 Page - Anachip Corp |
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PEEL18LV8ZSI-15L Datasheet(HTML) 3 Page - Anachip Corp |
3 / 10 page Anachip Corp. www.anachip.com.tw Rev. 1.0 Dec 16, 2004 3/10 Function Description The PEEL18LV8Z implements logic functions as sum-of- products expressions in a programmable-AND/fixed-OR logic array. Programming the connections of input signals into the array creates user-defined functions. User- configurable output structures in the form of I/O macrocells further increase logic flexibility. Architecture Overview The PEEL18LV8Z architecture is illustrated in the block diagram of Figure 14. Ten dedicated inputs and 8 I/Os provide up to 18 inputs and 8 outputs for creation of logic functions. At the core of the device is a programmable electrically erasable AND array that drives a fixed OR array. With this structure, the PEEL18LV8Z can implement up to 8 sum-of-products logic expressions. Associated with each of the 8 OR functions is an I/O macrocell that can be independently programmed to one of 12 different configurations. The programmable macrocells allow each I/O to be used to create sequential or combinatorial logic functions of active-high or active-low polarity, while providing three different feedback paths into the AND array. AND/OR Logic Array The programmable AND array of the PEEL18LV8Z (shown in Figure 15) is formed by input lines intersecting product terms. The input lines and product terms are used as follows: • 36 Input Lines: - 20 input lines carry the true and complement of the signals applied to the 10 input pins - 16 additional lines carry the true and complement values of feedback or input signals from the 8 I/Os • 113 product terms: - 102 product terms are used to form sum of product functions - 8 output enable terms (one for each I/O) - 1 global synchronous preset term - 1 global asynchronous clear term - 1 programmable clock term At each input-line/product-term intersection, there is an EEPROM memory cell that determines whether or not there is a logical connection at that intersection. Each product term is essentially a 36-input AND gate. A product term that is connected to both the true and complement of an input signal will always be FALSE and thus will not affect the OR function that it drives. When all the connections on a product term are opened, a "don't care" state exists and that term will always be TRUE. When programming the PEEL18LV8Z, the device programmer first performs a bulk erase to remove the previous pattern. The erase cycle opens every logical connection in the array. The device is configured to perform the user-defined function by programming selected connections in the AND array. (Note that PEEL device programmers automatically program all of the connections on unused product terms so that they will have no effect on the output function). Variable Product Term Distribution The PEEL18LV8Z provides 113 product terms to drive the 8 OR functions. These product terms are distributed among the outputs in groups of 8, 10, 12, 14, and 16 to form logical sums (see Figure 15). This distribution allows optimum use of the device resources. Programmable I/O Macrocell The unique twelve-configuration output macrocell provides complete control over the architecture of each output. The ability to configure each output independently lets you to tailor the configuration of the PEEL18LV8Z to the precise requirements of your design. Macrocell Architecture Each I/O macrocell, as shown in Figure 4, consists of a D- type flip-flop and two signal-select multiplexers. The four EEPROM bits controlling these multiplexers determine the configuration of each macrocell. These bits determine output polarity, output type (registered or non-registered) and input-feedback path (bidirectional I/O, combinatorial feedback). Refer to Table 1 for details. Equivalent circuits for the twelve macrocell configurations are illustrated in Figure 5. In addition to emulating the four PAL-type output structures (configurations 3, 4, 9, and 10), the macrocell provides eight additional configurations. When creating a PEEL device design, the desired macrocell configuration is generally specified explicitly in the design file. When the design is assembled or compiled, the macrocell configuration bits are defined in the last lines of the JEDEC programming file. Output Type The signal from the OR array can be fed directly to the output pin (combinatorial function) or latched in the D-type flip-flop (registered function). The D-type flip-flop latches data on the rising edge of the clock and is controlled by the global preset and clear terms. When the synchronous preset term is satisfied, the Q output of the register is set HIGH at the next rising edge of the clock input. Satisfying |
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