[英]Read certain bits from one register and write into certain bits of another
I am looking to implement the prototype for read_and_write, but couldn't get it right.我正在寻找实现 read_and_write 的原型,但无法正确实现。 Any help is appreciated.
任何帮助表示赞赏。 I am able to extract bits.
我能够提取位。
In this below code for write_val1, my intent is to write only the first 9 bits of final_val into read_data.在下面的 write_val1 代码中,我的目的是只将 final_val 的前 9 位写入 read_data。 The rest 7 bits of read_data should remain untouched.
read_data 的其余 7 位应保持不变。 Expected output for write_val1 = 0x0080
write_val1 的预期输出 = 0x0080
Similarly for write_val2, my intent is to write only next 8 bits from final_val into read_data.同样对于 write_val2,我的目的是只将 final_val 的下 8 位写入 read_data。 The rest 8 bits of read_data should remain untouched.
read_data 的其余 8 位应保持不变。 Expected output for write_val2 = 0x2700
write_val2 的预期输出 = 0x2700
Similarly for write_val3, my intent is to write only next 3 bits(010) from final_val into a position[11:13] of read_data leaving rest of read_data untouched.与 write_val3 类似,我的目的是只将 final_val 的下 3 位(010)写入 read_data 的位置 [11:13],而其余的 read_data 保持不变。
Expected output = 0x5448 ;
预期输出 = 0x5448 ; For example: pick 010 extracted bit from write_val3;
例如:pick 010 从 write_val3 中提取的位; 0x3048 = 01 11 0 000 0100 1000;
0x3048 = 01 11 0 000 0100 1000; 0x5048 = 01 01 0 000 0100 1000
0x5048 = 01 01 0 000 0100 1000
#include <stdio.h>
#include <stdint.h>
// Extracts n bits from a given position in LSB.
int bitExtracted(uint16_t read_data, uint8_t n_bits, uint8_t pos)
{
return (((1 << n_bits) - 1) & (read_data >> (pos - 1)));
}
void read_and_write(uint32_t* final_val, uint16_t* write_val, uint8_t start_pos, uint8_t end_pos)
{
uint32_t temp = *final_val;
*write_val = (uint16_t) ((temp >> start_pos) & ((1 << end_pos) - 1)); // store the desired number of bits in write_val
*final_val = (temp >> end_pos); //shift final_val by end_pos since those bits are already written
printf("\n temp %x, write_val %x, final_val %x ", temp, *write_val, *final_val);
}
void main()
{
uint16_t read_data = 0x0; //assume some read value
uint16_t ext_val1 = bitExtracted(read_data, 9, 1); //Read BITS [8:0] from read_data
uint8_t ext_val2 = bitExtracted(read_data, 8, 1); //Read BITS [7:0] from read_data
uint8_t ext_val3 = bitExtracted(read_data, 3, 5); //Read BITS [7:4] from read_data
uint32_t final_val = 0x0; //Stores 20 extracted bits from val1, val2 and val3 into final_val (LSB to MSB in order)
uint16_t write_val1, write_val2, write_val3;
uint8_t start_pos = 0, end_pos =8;
ext_val1 = 0x80, ext_val2 = 0x0, ext_val3 = 0x2;
final_val = (ext_val1 | (ext_val2 << 9) | (ext_val3 << 17));
printf ("\n final_val %x", final_val);
//Read first 9 bits of final_val and write only into [8:0] position of existing read_data
read_and_write(&final_val, &write_val1, 0, 9);
read_data = 0x80;
write_val1 = write_val1 | read_data;
//Read next 8 bits of final_val and write only into [7:0] position of existing read_data
start_pos = 0;
end_pos = 7;
read_data = 0x27b7;
read_and_write(&final_val, &write_val2, start_pos, end_pos);
write_val2 = write_val2 | read_data;
//Read next 3 bits of final_val and write only into[13:11] position of existing read_data
start_pos = 11;
end_pos = 13;
read_data = 0x3048;
read_and_write(&final_val, &write_val3, start_pos, end_pos);
write_val3 = write_val3 | read_data;
printf ("\n val1 0x%x val2 0x%x val3 0x%x final_val 0x%x", write_val1, write_val2, ext_val3, final_val);
}
If you want your read_and_write()
function to be able to change the values of the first two inputs to the function, (eg final_val
and write_val1
), then they should be passed as pointers to the function.如果您希望
read_and_write()
函数能够更改函数的前两个输入的值(例如final_val
和write_val1
),则应将它们作为指向函数的指针传递。 Your function prototype should thus look like this:因此,您的函数原型应如下所示:
void read_and_write(uint32_t* final_val, uint16* write_val1, uint8_t start_pos, uint8_t end_pos);
When calling the function in your main code, you need to use &
to take the address of the variables.在主代码中调用函数时,需要使用
&
来获取变量的地址。 So you call them using:因此,您可以使用以下方法调用它们:
read_and_write(&final_val, &write_val1, start_pos, end_pos);
For the reading and writing portion, it is pretty much similar to what you did in the bitExtracted
function.对于读取和写入部分,它与您在
bitExtracted
函数中所做的非常相似。
uint32_t temp = *final_val;
*write_val = (uint16_t) ((temp >> start_pos) & ((1 << end_pos) - 1)); // store the desired number of bits in write_val
*final_val = (temp >> end_pos); //shift final_val by end_pos since those bits are already written
The *
is to deference the pointer and access the data stored in a particular location. *
是为了尊重指针并访问存储在特定位置的数据。 Note that you also need to have a (uint16_t)
cast for write_val
since the type needs to match.请注意,您还需要对
write_val
进行(uint16_t)
write_val
因为类型需要匹配。
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