LSB优先还是MSB优先？ [英] LSB first or MSB first ?

问题描述

我想用十六进制数转换一个十进制数，然后先用LSB通过串口发送。



我试过这个

I want to convert a decimal number in hexadecimal number and send through serial port with LSB first.

I tried this

Int32 decValue = 1234056789;
byte[] testBytes = new byte[4];

    testBytes [0] = (byte)(decValue & 0x000000FF);
    testBytes [1] = (byte)((decValue >> 8) & 0x000000FF);
    testBytes [2] = (byte)((decValue >> 16) & 0x000000FF);
    testBytes [3] = (byte)((decValue >> 24) & 0x000000FF);

testBytes [0]是否包含LSB中的字节第一个或MSB优先???

Is testBytes[0] contains bytes in LSB first or MSB first???

推荐答案

严格来说，它取决于连接到RS-232电缆另一端的设备的要求。 Windows使用little-endian格式（最低有效字节优先）;我会说，大多数系统都是这样做的。但是，这不是一个规则; big-endian也被使用。例如，所谓的标准网络订单是big-endian。



请参阅： http://en.wikipedia.org/wiki/Endianness [ ^ ]。

-SA

Strictly speaking, it depends on the requirements of the device connected to the other end of your RS-232 cable. Windows uses "little-endian" formats (least significant byte goes first); I would say, most systems do the same. However, this is not a rule; "big-endian" is also used. For example, so-called standard "network order" is big-endian.

Please see: http://en.wikipedia.org/wiki/Endianness[^].

—SA

这是测试方法来自msdn： http://msdn.microsoft.com/en-us/library/bb384066 .aspx [ ^ ]

This is the way to test taken from msdn: http://msdn.microsoft.com/en-us/library/bb384066.aspx[^]

byte[] bytes = { 0, 0, 0, 25 };

int i = BitConverter.ToInt32(bytes, 0);
Console.WriteLine("int: {0}", i);

如果这打印25，那么你的计算机是big-endian - 你首先发送testBytes [3]。

如果它不打印25然后发送testBytes [ 0]首先。



但是有一个对endian_ness BitConverter.IsLittleEndian的测试。所以你可以写：

If this prints 25 then your computer is big-endian - you send testBytes [3] first.
If it does not print 25 then send testBytes [0] first.

There is however a test for endian_ness BitConverter.IsLittleEndian. So you can write:

byte[] bytes = { 0, 0, 0, 25 };

// If the system architecture is little-endian (that is, little end first), 
// reverse the byte array. 
if (BitConverter.IsLittleEndian)
    Array.Reverse(bytes);

int i = BitConverter.ToInt32(bytes, 0);
Console.WriteLine("int: {0}", i);
// Output: int: 25

您还应该查看BitConverter.GetBytes（Int32）以将Int32转换为字节数组。

http://msdn.microsoft.com/en-us/library/de8fssa4(v=vs.110).aspx [ ^ ]

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