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MPC750A RISC Microprocessor Hardware Specifications

System Design Information

1.8.1 PLL Configuration

The MPC750’s PLL is configured by the PLL_CFG[0–3] 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 MPC750 is shown in Table 17 for nominal frequencies.

Table 17. MPC750 Microprocessor PLL Configuration

PLL_CFG

[0–3]

Sample Bus-to-Core Frequency in MHz (VCO Frequency in MHz)

Bus-to-

Core

Multiplier

Core-to

VCO

Multiplier

Bus

25 MHz

Bus

33.3

MHz

Bus

40 MHz

Bus

50 MHz

Bus

66.6

MHz

Bus

75 MHz

Bus

83.3

MHz

1000

3x

2x

150 (300) 200

(400)

225 (450) 250

(500)

1110

3.5x

2x

175 (350) 233

(466)

262 (525)

1010

4x

2x

160 (320) 200 (400) 266

(533)

0111

4.5x

2x

150

(300)

180 (360) 225 (450)

1011

5x

2x

166

(333)

200 (400) 250 (500)

1001

5.5x

2x

183

(366)

220 (440)

1101

6x

2x

150 (300) 200

(400)

240 (480)

0101

6.5x

2x

162 (325) 216

(433)

260 (520)

0010

7x

2x

175 (350) 233

(466)

0001

7.5x

2x

187

(375)

250

(500)

1100

8x

2x

200

(400)

266

(533)

0011

PLL off/bypass

PLL off, SYSCLK clocks core circuitry directly, 1x bus-to-core implied

1111

PLL off

PLL off, no core clocking occurs

Notes:

1. PLL_CFG[0–3] settings not listed are reserved.

2. The sample bus-to-core frequencies shown are for reference only. Some PLL configurations may select bus, core, or VCO

frequencies which are not useful, not supported, or not tested for by the MPC750; see Section 1.4.2.1, “Clock AC

Specifications,” for valid SYSCLK and VCO frequencies.

3. In PLL-bypass mode, the SYSCLK input signal clocks the internal processor directly, the PLL is disabled, and the bus mode is

set for 1:1 mode operation. This mode is intended for factory use only.

Note: The AC timing specifications given in this document do not apply in PLL-bypass mode.

4. In clock-off mode, no clocking occurs inside the MPC750 regardless of the SYSCLK input.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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