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常見問答
Why did the phenomenon of data sent by PDMA being displaced occur? Issue Date：2016-06-27
When the source or destination address is set as the array starting address, the user must check whether the array starting address is word aligned.
In the following example, the starting address of a buffer is 0x2000_0039. Since the ordering of memory is determined by a compiler, the non-word aligned situation may occur.
unsigned int test2;
unsigned char test1;
unsigned char buffer[100];
When the PDMA source or destination address is set as buffer (0x2000_0039), PDMA hardware will be set as word accessed (0x2000_0038).
If using the PDMA with UART to send data, the data to be sent will be 0x01, 0x03 …, instead of starting from 0X03.
In the case that memory is not word aligned, aligned (4) can be used such that the array can be aligned with the byte in memory.
unsigned char buffer[100] __attribute__ ((aligned (4)));
The starting address of the array buffer will be arranged and aligned with 4 bytes.
When the PDMA source or destination address is set as buffer (0x2000_003C), there are words being aligned. If using the PDMA with UART to send data, the data to be sent will start from 0X03.
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| Applications: | |
| Function: | Peripherals,Connectivity,DMA (PDMA) |