參數(shù)資料
型號: MC7445ARX733LG
廠商: MOTOROLA INC
元件分類: 微控制器/微處理器
英文描述: 32-BIT, 733 MHz, RISC PROCESSOR, CBGA360
封裝: 25 X 25 MM, 1.27 MM PITCH, CERAMIC, BGA-360
文件頁數(shù): 14/76頁
文件大?。?/td> 1520K
代理商: MC7445ARX733LG
MOTOROLA
MPC7455 RISC Microprocessor Hardware Specifications
21
Electrical and Thermal Characteristics
The L3_CLK timing diagram is shown in Figure 7.
Figure 7. L3_CLK_OUT Output Timing Diagram
1.5.2.4
L3 Bus AC Specifications
The MPC7455 L3 interface supports three different types of SRAM: source-synchronous, double data rate
(DDR) MSUG2 SRAM, late write SRAMs, and pipeline burst (PB2) SRAMs. Each requires a different
protocol on the L3 interface and a different routing of the L3 clock signals. The type of SRAM is
programmed in L3CR[22:23] and the MPC7455 then follows the appropriate protocol for that type. The
designer must connect and route the L3 signals appropriately for each type of SRAM. Following are some
observations about the chip-to-SRAM interface.
The routing for the point-to-point signals (L3_CLK[0:1], L3DATA[0:63], L3DP[0:7], and
L3_ECHO_CLK[0:3]) to a particular SRAM should be delay matched. If necessary, the length of
traces can be altered in order to intentionally skew the timing and provide additional setup or hold
time margin.
For a 1-Mbyte L3, use address bits 16:0 (bit 0 is LSB).
No pull-up resistors are required for the L3 interface.
For high speed operations, L3 interface address and control signals should be a ‘T’ with minimal
stubs to the two loads; data and clock signals should be point-to-point to their single load. Figure 8
shows the AC test load for the L3 interface.
Figure 8. AC Test Load for the L3 Interface
In general, if routing is short, delay-matched, and designed for incident wave reception and minimal
reflection, there is a high probability that the AC timing of the MPC7455 L3 interface will meet the
maximum frequency operation of appropriately chosen SRAMs. This is despite the pessimistic,
guard-banded AC specifications (see Table 12, Table 13, and Table 14), the limitations of functional testers
L3_CLK0
VM
tL3CR
tL3CF
VM
L3_CLK1
VM
tL3_CLK
tCHCL
VM
tL3CSKW1
L3_ECHO_CLK1
L3_ECHO_CLK3
VM
tL3CSKW2
VM
tL3CSKW2
For PB2 or Late Write:
Output
Z0 = 50
GVDD/2
RL = 50
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