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2019年12月18日

Tips on how to parity Memory

parity verify of memory. During the host method, it reads and writes memory and information A check circuit checks whether the knowledge composed to the key memory matches the data read through. If it doesn't match, the CpU is notified of a crash by a pressured interrupt (NMI) circuit.


When the CpU writes knowledge to primary memory, in addition it sends the information into the parity bit master / checker (74280) for calculation. The 74280 chip can be a 9-bit parity little bit generator, but it's also a checker. The truth is, its key function will be to incorporate the H sign (high-level signal, that's, the "1" signal) input with the CpU on the DRAM memory to check out whether it's a fair number of "1" or an odd quantity of "1". Then output from its Even (odd) or Odd (odd) pin, the output signal will be the parity bit. If the CpU writes 8-bit knowledge into the major memory, it truly is calculated via the parity generator in the same time. Should the outcome with the calculation is really an even variety of "1", the parity bit is "1". Whether it is an odd range of "1" 1  the parity bit is L signal (lower degree, that's,?° 0 ?±signal), this parity bit is distributed towards the ninth memory chip for non permanent storage, which is, write When coming into details, a parity little bit is created, and no parity verify is carried out. Since there is no option for comparison examine, the parity bit of the producer could be "1" when composing. ", Might also be" 0 ". Inside the circuit of the personal computer AT, when the CpU reads the main memory, the 8-bit knowledge is additional to the parity little bit stored during the ninth memory chip just now. The received answer ought to be an odd variety of "1" (which is, the parity bit of the odd test circuit = "0"). Whether it is an even variety of "1", the parity check circuit is commenced, plus the CpU is notified by way of the NMI circuit. Therefore, the parity look at is made by the operator when looking at the data, for the reason that only when reading, can the data during the memory just penned be checked for faults.


The parity verify circuit is often checked in two strategies:


(one) Odd parity check out
(two) Even parity check out


can be an odd parity check out inside the pc host circuit, which is, the Even output on the parity bit need to be "0" when examine. When the parity little bit is "1", a parity error is going to be created, plus the CpU are going to be notified with the crash because of the NMI circuit. Throughout inspection, each parity little bit generator / checker (74280) chip can only check eight bits, see the quantity of bits your CpU has, then there are many teams of 74280, the host of pentium CpU has eight 7428O, but now all are reduced into the chipset, so a person team is utilized to explain the odd check How even parity examining will work.


parity test


one. When the CpU writes information to your memory, only parity bits are produced, and no parity bit test is carried out.


If the CpU writes info (8 bits), the 8 bits are included by the parity little bit generator, and also the calculation final result is as follows:


(one) When there is an even variety of "1", the parity little bit = one.
(two) If there are actually an odd amount of "1" s, the parity little bit = 0.


(three) The parity little bit is stored inside the ninth memory chip.


two. In the event the CpU reads the memory data, it compares while using the facts just penned at the moment and performs a parity examine.


(one) The info just prepared has an excellent number of "1" s additionally the parity little bit = "l" stored from the ninth memory chip, then calculated with the parity checker and logic circuit, Even connects The output from the pin must be an odd range of "1", that is definitely, the parity bit is "0".


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(two) The data just composed has an odd amount of "1" moreover the parity bit = "0" stored within the ninth memory chip, after which calculated via the parity checker and logic circuit, Even pin The output of continues to be an odd variety of "1", that is certainly, the parity bit is "0".


(3) So whether the knowledge just written has a fair quantity of "1" or an odd range of "1" when studying, it can be constantly a set odd variety of "1". If it is even, the system generates a sequence of operations Notify the CpU of a crash.


three. At present, most motherboards aid DRAM memory without parity. The technique BIOS will disable the parity purpose. The more recent BIOS will routinely detect if the motherboard's DRAM memory provides a parity.


4. Odd parity: D0  D7 add up an odd number of  The 74280 Even pin outputs  as the parity bit.


5. Even parity: D0  D7 insert up an excellent quantity of  The 74280Odd pin outputs as being the parity bit.


6. Odd parity examine: When reading through knowledge, D0  D7 additionally the parity little bit are calculated by 74280. If you'll find an odd quantity of s, the Even pin outputs  and also the Odd pin outputs  Whether it is a fair quantity of "1". Then the Even pin outputs "1" as well as Odd pin outputs "0".


7. When studying facts with even parity check, D0  D7 in addition parity digits are calculated by 74280. When there is a fair variety of  Even pin outputs and Odd pin outputs  . If it is an odd variety of "l", the Even pin outputs "0" along with the Odd pin outputs "1".


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