參數(shù)資料
型號: HMS30C7202N
廠商: Electronic Theatre Controls, Inc.
英文描述: Highly-intergrated MPU
中文描述: 高intergrated微處理器
文件頁數(shù): 48/179頁
文件大?。?/td> 2127K
代理商: HMS30C7202N
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HMS30C7202N
2004 MagnaChip Semiconductor Ltd. All Rights Reserved. Version 1.1
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are being transferred to SDRAM. The quad word buffer currently being written to may be accessed with non-
contiguous word, half word or byte writes, which will be merged into a single quad word. The buffered quad
word will be transferred to the SDRAM when:
z
There is a write to an SDRAM address outside the current quad word being merged into
z
There is a read to the address of the quad word being merged into
z
There is a time-out on the write back timer
The two quad-words that make up the write buffer operate in "ping-pong" fashion, whereby one is initially
designated the buffer for writes to go into, and the other is the buffer for write backs. When one of the three
events that can cause a write-back occurs, the functions of the two buffers are swapped. Thus the buffer
containing data to be written back becomes the buffer that is currently writing back, and the buffer that was the
write-back buffer becomes the buffer being written to.
In the case of a write-back initiated by a read from the same address as the data in the merge buffer, the quad
word in the buffer is written to SDRAM, and then the read occurs from SDRAM. The write before read is
essential, because not all of the quad word in the buffer may have been updated, so its contents need to be
merged with the SDRAM contents to fill any gaps where the buffer was not updated. The write buffer flush
timer forces a write back to occur after a programmable amount of time. Every time a write into the buffer
occurs, the counter is re-loaded with the programmed time-out value, and starts to counts down. If a time-out
occurs, then data in the write buffer is written to SDRAM.
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