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MPC8349ECVVALDB 数据表(PDF) 82 Page - Freescale Semiconductor, Inc |
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MPC8349ECVVALDB 数据表(HTML) 82 Page - Freescale Semiconductor, Inc |
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82 / 87 page ![]() MPC8349EA PowerQUICC II Pro Integrated Host Processor Hardware Specifications, Rev. 13 82 Freescale Semiconductor Ordering Information V2 =(1 ÷ (1/R1 +1/R2)) × Isource. Solving for the output impedance gives Rsource = Rterm × (V1 ÷ V2 –1). The drive current is then Isource =V1 ÷ Rsource. Table 65 summarizes the signal impedance targets. The driver impedance are targeted at minimum VDD, nominal OVDD, 105°C. 21.6 Configuration Pin Multiplexing The MPC8349EA power-on configuration options can be set through external pull-up or pull-down resistors of 4.7 k Ω on certain output pins (see the customer-visible configuration pins). These pins are used as output only pins in normal operation. However, while HRESET is asserted, these pins are treated as inputs, and the value on these pins is latched when PORESET deasserts. Then the input receiver is disabled and the I/O circuit takes on its normal function. Careful board layout with stubless connections to these pull-up/pull-down resistors coupled with the large value of the pull-up/pull-down resistor should minimize the disruption of signal quality or speed for the output pins. 21.7 Pull-Up Resistor Requirements The MPC8349EA requires high resistance pull-up resistors (10 k Ω is recommended) on open-drain pins, including I2C pins, and IPIC interrupt pins. For more information on required pull-up resistors and the connections required for the JTAG interface, refer to application note AN2931, “PowerQUICC Design Checklist.” 22 Ordering Information This section presents ordering information for the device discussed in this document, and it shows an example of how the parts are marked. NOTE The information in this document is accurate for revision 3.x silicon and later (in other words, for orderable part numbers ending in A or B). For information on revision 1.1 silicon and earlier versions, see the MPC8349E PowerQUICC II Pro Integrated Host Processor Hardware Specifications (Document Order No. MPC8349EEC). Table 65. Impedance Characteristics Impedance Local Bus, Ethernet, DUART, Control, Configuration, Power Management PCI Signals (Not Including PCI Output Clocks) PCI Output Clocks (Including PCI_SYNC_OUT) DDR DRAM Symbol Unit RN 42 Target 25 Target 42 Target 20 Target Z0 W RP 42 Target 25 Target 42 Target 20 Target Z0 W Differential NA NA NA NA ZDIFF W Note: Nominal supply voltages. See Table 1, Tj = 105°C. |
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