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MPC7448 RISC Microprocessor Hardware Specifications, Rev. 4

Freescale Semiconductor 35

System Design Information

9 System Design Information

This section provides system and thermal design requirements and recommendations for successful

application of the MPC7448.

9.1 Clocks

The following sections provide more detailed information regarding the clocking of the MPC7448.

9.1.1 PLL Configuration

The MPC7448 PLL is configured by the PLL_CFG[0:5] signals. For a given SYSCLK (bus) frequency,

the PLL configuration signals set the internal CPU and VCO frequency of operation. The PLL

configuration for the MPC7448 is shown in Table 12. In this example, shaded cells represent settings that,

for a given SYSCLK frequency, result in core and/or VCO frequencies that do not comply with Table 8.

When enabled, dynamic frequency switching (DFS) also affects the core frequency by halving or

quartering the bus-to-core multiplier; see Section 9.7.5, “Dynamic Frequency Switching (DFS),” for more

information. Note that when DFS is enabled the resulting core frequency must meet the adjusted minimum

core frequency requirements (f

core_DFS

) described in Table 8. Note that the PLL_CFG[5] is currently used

for factory test only and should be tied low, and that the MPC7448 PLL configuration settings are

compatible with the MPC7447A PLL configuration settings when PLL_CFG[5] = 0.

Table 12. MPC7448 Microprocessor PLL Configuration Example

PLL_CFG[0:5]

Example Core and VCO Frequency in MHz

Bus-to-Core

Multiplier

Core-to-VCO

Multiplier

Bus (SYSCLK) Frequency

33.3

MHz

66.6

MHz

100

MHz

133

MHz

167

MHz

200

MHz

010000 2x

100000 3x

1x 600

101000 4x

1x 667 800

101100 5x 1x

667 835 1000

100100 5.5x 1x

733 919 1100

110100 6x 1x

600 800 1002 1200

010100 6.5x 1x

650 866 1086 1300

001000 7x 1x

700 931 1169 1400

000100 7.5x 1x

623 750 1000 1253 1500

110000 8x 1x

600 664 800 1064 1336 1600

011000 8.5x 1x

638 706 850 1131 1417 1700

011110 9x 1x

600 675 747 900 1197 1500

011100 9.5x 1x 633 712 789 950 1264 1583

101010 10x 1x 667 750 830 1000 1333 1667

100010 10.5x 1x 700 938 872 1050 1397

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 59 60

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