參數(shù)資料
型號: SCF5250VM120
廠商: Motorola, Inc.
英文描述: SCF5250 Integrated ColdFire Microprocessor
中文描述: SCF5250提供了集成的ColdFire微處理器
文件頁數(shù): 13/48頁
文件大?。?/td> 767K
代理商: SCF5250VM120
Signal Descriptions
SCF5250 Integrated ColdFire Microprocessor Data Sheet, Rev. 1.1
Freescale Semiconductor
13
4.3.1
Address Bus
The address bus provides the address of the byte or most significant byte of the word or longword
being transferred.The address lines also serve as the DRAM address pins, providing multiplexed
row and column address signals.
Bits 23 down to 1 and 24 of the address are available. A24 is intended to be used with 256 Mbit
DRAM’s. Signals are named:
— A[23:1]
— A20/24
4.3.2
Read-Write Control
This signal indicates during any bus cycle whether a read or write is in progress. A low is write cycle and
a high is a read cycle.
4.3.3
Output Enable
The OE signal is intended to be connected to the output enable of asynchronous memories connected to
chip selects. During bus read cycles, the ColdFire processor will drive OE low.
4.3.4
Data Bus
The data bus (D[31:16]) is bi-directional and non-multiplexed. Data is registered by the SCF5250 on the
rising clock edge. The data bus uses a default configuration if none of the chip-selects or DRAM bank
match the address decode. All 16 bits of the data bus are driven during writes, regardless of port width or
operand size.
4.3.5
Transfer Acknowledge
The TA/GPIO12 pin is the transfer acknowledge signal.
4.4
SDRAM Controller Signals
The following SDRAM signals provide a glueless interface to external SDRAM. An SDRAM width of 16
bits is supported and can access as much as 32MB of memory. ADRAMs are not supported.
Table 4. SDRAM Controller Signals
SDRAM Signal
Description
Synchronous DRAM row address strobe
The SDRAS/GPIO59 active low pin provides a seamless interface to the
RAS input on synchronous DRAM
Synchronous DRAM Column Address StrobeThe SDCAS/GPIO39 active low pin provides a seamless interface to
CAS input on synchronous DRAM.
Synchronous DRAM Write
The SDWE/GPIO38 active-low pin is asserted to signify that a SDRAM
write cycle is underway. This pin outputs logic ‘1’ during read bus cycles.
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