Re: PIC32有分省不省電嗎?

作者 timijk 於 2017年04月26日 14:42:41
如果你沒有提到這 AGU 的問題 我也沒注意到

其實 X AGU 跟 Y AGU 並不是說 X AGU 只能定址到 X memory

Y AGU 是有限制 只能用來 讀 Y memory... 他使用得場合是在 DSP 指令 如 MAC 和 MPY 時 同步讀取資料用的 所以沒有寫入Y memory 的功能

X AGU 是可以定址到全域 包含 Y memory, 只有在 DSP 指令時 同步讀取資料時 只能指到 X memory

如果你看一下 CPU 的架構圖 你可以發現 X RAGU/WAGU 是可以定址到 Y memory (如附檔)

詳細的說明在 FRM Data Memory 章節裡面... 節錄如下

Section 3 Data Memory
3.3 Data Space Address
The X AGU is used by all instructions and supports all addressing modes. The X AGU consists
of a read AGU (X RAGU) and a write AGU (X WAGU), which operate independently on separate
read and write buses during different phases of the instruction cycle. The X read data bus is the
return data path for all instructions that view data space as combined X and Y address space. It
is also the X address space data path for the dual operand read instructions (DSP instruction
class). The X write data bus is the only write path to the combined X and Y data space for all
instructions.
...
The Y data memory space has one AGU that supports data reads from the Y data memory space.
The Y memory bus is never used for data writes. The function of the Y AGU and Y memory bus
is to support concurrent data reads for DSP class instructions.

附加檔案:



jpg  AGU.JPG (51.25 KB)
4050_59003df981787.jpg 487X461 px

來自: http://www.microchip.com.tw/newbb/viewtopic.php?forum=8&topic_id=20112&post_id=75003