参数资料
型号: MC7457RX1000NC
厂商: Freescale Semiconductor
文件页数: 48/71页
文件大小: 0K
描述: IC MPU RISC 32BIT 483FCCBGA
标准包装: 36
系列: MPC74xx
处理器类型: 32-位 MPC74xx PowerPC
速度: 1.0GHz
电压: 1.1V
安装类型: 表面贴装
封装/外壳: 483-BCBGA,FCCBGA
供应商设备封装: 483-FCCBGA(29x29)
包装: 托盘
MPC7457 RISC Microprocessor Hardware Specifications, Rev. 8
System Design Information
Freescale Semiconductor
52
9.1.2
L3 Clocks
The MPC7457 generates the clock for the external L3 synchronous data SRAMs by dividing the core clock
frequency of the MPC7457. The core-to-L3 frequency divisor for the L3 PLL is selected through the
L3_CLK bits of the L3CR register. Generally, the divisor must be chosen according to the frequency
supported by the external RAMs, the frequency of the MPC7457 core, and timing analysis of the circuit
board routing. Table 19 shows various example L3 clock frequencies that can be obtained for a given set
of core frequencies.
11110
PLL off
PLL off, no core clocking occurs
Notes:
1. PLL_CFG[0:4] 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 MPC7455; see Section 5.2.1, “Clock AC
Specifications,for valid SYSCLK, core, and VCO frequencies.
3. In PLL-bypass mode, the SYSCLK input signal clocks the internal processor directly and the PLL is disabled. However,
the bus interface unit requires a 2x clock to function. Therefore, an additional signal, EXT_QUAL, must be driven at
one-half the frequency of SYSCLK and offset in phase to meet the required input setup tIVKH and hold time tIXKH (see
Table 9). The result is that the processor bus frequency is one-half SYSCLK while the internal processor is clocked at
SYSCLK frequency. This mode is intended for factory use and emulator tool use only.
Note: The AC timing specifications given in this document do not apply in PLL-bypass mode.
4. In PLL-off mode, no clocking occurs inside the MPC7455 regardless of the SYSCLK input.
Table 19. Sample Core-to-L3 Frequencies 1
Core
Frequency
(MHz) 2
÷2
÷2.5
÷3
÷3.5
÷4
÷4.5
÷5
÷5.5
÷6
÷6.5
÷7
÷7.5
÷8
500
250
200
167
143
125
111
100
91
83
77
71
67
63
533
266
213
178
152
133
118
107
97
89
82
76
71
67
550
275
220
183
157
138
122
110
100
92
85
79
73
69
600
300
240
200
171
150
133
120
109
100
92
86
80
75
650
325
260
217
186
163
144
130
118
108
100
93
87
81
666
333
266
222
190
167
148
133
121
111
102
95
89
83
700
350
280
233
200
175
156
140
127
117
108
100
93
88
733
367
293
244
209
183
163
147
133
122
113
105
98
92
800
400
320
266
230
200
178
160
145
133
123
114
107
100
866
433
347
289
248
217
192
173
157
145
133
124
115
108
933
467
373
311
266
233
207
187
170
156
144
133
124
117
1000
500
400
333
285
250
222
200
182
166
154
143
133
125
Table 18. MPC7457 Microprocessor PLL Configuration Example for 1267 MHz Parts (continued)
PLL_CFG[0:4]
Bus-to-
Core
Multiplier
Core-to-
VCO
Multiplier
Example Bus-to-Core Frequency in MHz (VCO Frequency in MHz)
Bus (SYSCLK) Frequency
33.3
MHz
50
MHz
66.6
MHz
75
MHz
83
MHz
100
MHz
133
MHz
167
MHz
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