That is the BCD code. Binary-Coded Decimal, referred to as BCD, is called BCD code or binary-decimal code, also known as binary code decimal. It is a form of binary digital encoding, with binary coded decimal code. This coding format uses four bits to store a decimal number, so that the conversion between binary and decimal can be carried out quickly. This coding technique is most commonly used in the design of accounting systems, because accounting systems often require accurate calculations for very long strings of numbers. Compared with the general floating-point notation, the BCD code can be used to save the accuracy of the value and avoid the time spent by the computer for floating-point operations. In addition, for other calculations that require high accuracy, BCD coding is also commonly used.
Since the decimal number has 0, 1, 2, ., 9 ten digits, at least 4 binary codes are needed to represent 1 decimal number. When using BCD encoding, it must be noted that there are only ten effective encodings, namely: 0000~1001. The remaining six encodings of four-bit binary numbers 1010, 1011, 1100, 1101, 1110, 1111 are not effective encodings. Common BCD codes are 8421BCD code, 2421BCD code, the remaining 3 codes, the corresponding coding table is as follows。
BCD is a monolithic integrated process technology. It was first developed by STMicroelectronics (ST) in 1986. This technology can produce bipolar, CMOS and DMOS devices on the same chip, which is called the BCD process.
The BCD process simultaneously manufactures bipolar devices and CMOS devices on the same chip. It combines the advantages of bipolar devices with high transconductance, strong load drive capability, high CMOS integration, and low power consumption, so that they can learn from each other's strengths and weaknesses, and play to their respective advantages. More importantly, it integrates DMOS power devices, DMOS can work in switching mode, and the power consumption is extremely low. No expensive packaging and cooling systems are required to transfer high power to the load. Low power consumption is one of the main advantages of the BCD process. The integrated BCD process can greatly reduce power consumption, improve system performance, save circuit packaging costs, and have better reliability.
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