Programming tricks

-

  1. Swap the contents of two registers.
    XOR R0, R1
    XOR R1, R0
    XOR R0, R1
    Remember "1" in result means differences, while "0" means same. However when the number apears in operation of XOR, "1" means reverse and "0" means keep.
  2. To judge if two numbers are equal, we can also use XOR.
    XOR R0, R1
    If the result is 0, then R0 and R1 are equal. Otherwise they are not.
  3. Struct type allows the specification of elements of a structure into a fixed number of bits.
    struct fivebits
    {
        unsigned int flag : 1;     // act as switch, on (1) or off (0)
        signed int num   : 4; // number ranges from -8...7
                                : 3; // empty 3 bits used to align to 8bits, this is necessary for manipulation
    }

Comments

Post a Comment

Popular posts from this blog

Basic understanding of TLS-PSK protocol

-
Image
This post will talk about the basic understanding of TLS-PSK protocol. It will not cover TLS's history and how its mathematical algorithms work. Instead, what is TLS-PSK protocol and how it works will be discussed here. I prefer using diagrams to help explain things. Hopefully, it can give readers a very basic insights of TLS-PSK. What is TLS-PSK Before talking about what is TLS-PSK, I would like to introduce what is TLS first. TLS, Transport Layer Security, is a cryptographic protocol, aims to provide protection to end-to-end communication over the internet. It helps to protect network users from eavesdropping, tempering and so on. Clear data transmission is dangerous, given that technical hacker can listen to the communication between two computers and steal sensitive data like user name, password and so on. This is situation where TLS can step in and protect you. TLS has two steps: TLS handshake and data transmission. During TLS handshake, the communicating parties mus...
Read more

Differences between ASIC, ASSP and ASIP

-
ASIC (Application Specified Integrated Circuit) is a customized integrated circuit. It is usually used by a person or company for a very limited usage. So when it is developed, only the person or company who orders it can use it. It is not useful for other usages, for example, an IC designed for a specific line of cellular phones of a company, whereby no other products can use it except the cell phones belonging to that product line. - ASIC is just built for one and only one customer. - ASIC is used only in one product line - Only volume production of ASICs for one product can make sense which means low unit cost for high volume products, otherwise the cost is not efficient. - Can exploit parallelism to achieve high performance - Low power consumption ASSP (Application Specified Standard Processor) is an integrated circuit that implements a specific function that appeals to a wide market, which means its function is specified for example a motor drive chip. But it is used widel...
Read more

Orthogonal instruction set

-
Definition: "In computer engineering, an orthogonal instruction set is an instruction set architecture where  all instruction types  can use  all addressing modes . It is 'orthogonal' in the sense that the instruction type and the addressing mode vary independently." The story of orthogonal instruction set: In the past, because the  memory is very precious , so the processor designer tends to  make instructions as powerful as possible . So they hope one instruction can perform  full function  like get data from memory and then perform the calculation. They make  all instructions can have all the addressing modes . By this way,  one instruction can fetch data and do the calculation at the same time .  But this will  inscrease the complexity  of the processor design. Also, accessing memory directly is very time-consuming, so some companies choose to use RISC processor (like ARM) which has a  LOAD-STORE a...
Read more