MPC8358E datasheet(93/96 Pages) FREESCALE

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MPC8358E PowerQUICC™ II Pro Processor Revision 2.1 PBGA Silicon Hardware Specifications, Rev. 1

Freescale Semiconductor

System Design Information

Figure 54. Driver Impedance Measurement

The value of this resistance and the strength of the driver’s current source can be found by making two

measurements. First, the output voltage is measured while driving logic 1 without an external differential

termination resistor. The measured voltage is V1 = Rsource × Isource. Second, the output voltage is measured

while driving logic 1 with an external precision differential termination resistor of value Rterm. The

measured voltage is V2 = 1/(1/R1 +1/R2)) × Isource. Solving for the output impedance gives Rsource = Rterm

× (V

1/V2 – 1). The drive current is then Isource =V1/Rsource.

Table 77 summarizes the signal impedance targets. The driver impedance are targeted at minimum VDD,

nominal OVDD, 105°C.

24.6

Configuration Pin Muxing

The device provides the user with power-on configuration options which can be set through the use of

external pull-up or pull-down resistors of 4.7 k

Ω on certain output pins (see customer visible configuration

pins). These pins are generally used as output only pins in normal operation.

While HRESET is asserted however, these pins are treated as inputs. The value presented on these pins

while HRESET is asserted, is latched when HRESET deasserts, at which time the input receiver is disabled

Table 77. Impedance Characteristics

Impedance

Local Bus, Ethernet,

DUART, Control,

Configuration, Power

Management

PCI

DDR DRAM

Symbol

Unit

42 Target

25 Target

20 Target

42 Target

25 Target

20 Target

Differential

ZDIFF

Note: Nominal supply voltages. See Table 1, TJ = 105°C.

OVDD

OGND

Pad

Data

SW1

SW2

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