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LCMXO2-256ZE-2MG132C 数据表(PDF) 26 Page - Lattice Semiconductor |
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LCMXO2-256ZE-2MG132C 数据表(HTML) 26 Page - Lattice Semiconductor |
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26 / 106 page  2-22 Architecture MachXO2 Family Data Sheet Block, to facilitate the generation of clock and control signals (DQSR90, DQSW90, DDRCLKPOL and DATAVALID). These clock and control signals are distributed to the other PIO in the group through dedicated low skew routing. DQS Read Write Block Source synchronous interfaces generally require the input clock to be adjusted in order to correctly capture data at the input register. For most interfaces a PLL is used for this adjustment. However, in DDR memories the clock (referred to as DQS) is not free-running so this approach cannot be used. The DQS Read Write block provides the required clock alignment for DDR memory interfaces. DQSR90 and DQSW90 signals are generated by the DQS Read Write block from the DQS input. In a typical DDR memory interface design, the phase relationship between the incoming delayed DQS strobe and the internal system clock (during the read cycle) is unknown. The MachXO2 family contains dedicated circuits to transfer data between these domains. To prevent set-up and hold violations, at the domain transfer between DQS (delayed) and the system clock, a clock polarity selector is used. This circuit changes the edge on which the data is registered in the synchronizing registers in the input register block. This requires evaluation at the start of each read cycle for the correct clock polarity. Prior to the read operation in DDR memories, DQS is in tri-state (pulled by termination). The DDR memory device drives DQS low at the start of the preamble state. A dedicated circuit in the DQS Read Write block detects the first DQS rising edge after the preamble state and generates the DDRCLKPOL signal. This signal is used to control the polarity of the clock to the synchronizing registers. The temperature, voltage and process variations of the DQS delay block are compensated by a set of calibration signals (6-bit bus) from a DLL on the right edge of the device. The DLL loop is compensated for temperature, volt- age and process variations by the system clock and feedback loop. sysIO Buffer Each I/O is associated with a flexible buffer referred to as a sysIO buffer. These buffers are arranged around the periphery of the device in groups referred to as banks. The sysIO buffers allow users to implement a wide variety of standards that are found in today’s systems including LVCMOS, TTL, PCI, SSTL, HSTL, LVDS, BLVDS, MLVDS and LVPECL. Each bank is capable of supporting multiple I/O standards. In the MachXO2 devices, single-ended output buffers, ratioed input buffers (LVTTL, LVCMOS and PCI), differential (LVDS) and referenced input buffers (SSTL and HSTL) are powered using I/O supply voltage (VCCIO). Each sysIO bank has its own VCCIO. In addition, each bank has a voltage reference, VREF, which allows the use of referenced input buffers independent of the bank VCCIO. MachXO2-256 and MachXO2-640 devices contain single-ended ratioed input buffers and single-ended output buf- fers with complementary outputs on all the I/O banks. Note that the single-ended input buffers on these devices do not contain PCI clamps. In addition to the single-ended I/O buffers these two devices also have differential and ref- erenced input buffers on all I/Os. The I/Os are arranged in pairs, the two pads in the pair are described as “T” and “C”, where the true pad is associated with the positive side of the differential input buffer and the comp (comple- mentary) pad is associated with the negative side of the differential input buffer. MachXO2-640U, MachXO2-1200/U, MachXO2-2000/U, MachXO2-4000 and MachXO2-7000 devices contain three types of sysIO buffer pairs. 1. Left and Right sysIO Buffer Pairs The sysIO buffer pairs in the left and right banks of the device consist of two single-ended output drivers and two single-ended input buffers (for ratioed inputs such as LVCMOS and LVTTL). The I/O pairs on the left and right of the devices also have differential and referenced input buffers. 2. Bottom sysIO Buffer Pairs The sysIO buffer pairs in the bottom bank of the device consist of two single-ended output drivers and two sin- gle-ended input buffers (for ratioed inputs such as LVCMOS and LVTTL). The I/O pairs on the bottom also have differential and referenced input buffers. Only the I/Os on the bottom banks have programmable PCI clamps |
类似零件编号 - LCMXO2-256ZE-2MG132C |
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类似说明 - LCMXO2-256ZE-2MG132C |
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