The timing generator is a thing similar to work and rest time in the CPU, which enables the computer to work accurately, quickly and orderly.Once the machine is started, that is, when the CPU starts to fetch instructions and execute them,Operation controllerUse the sequence of timing pulses and different pulse intervals to command the action of the machine in an orderly and rhythmic manner, specify what to do when this pulse arrives, and what to do when that pulse arrives, and provide time marks for each part of the computer to work.
A CPU like "work and rest time"thingSo that the computer can work accurately, quickly and orderly.Once the machine is started, that is, when the CPU starts to fetch instructions and execute them,Operation controllerUse the sequence of timing pulses and different pulse intervals to command the action of the machine in an orderly and rhythmic manner, specify what to do when this pulse arrives, and what to do when that pulse arrives, and provide time marks for each part of the computer to work.Therefore, it is necessary to adopt multi-level timing system.In terms of time, the command fetching event occurs in theInstruction cycleThe first CPU cycle of the instruction cycle occurs in the "instruction fetching" phase, while the data fetching event occurs in the following CPU cycles of the instruction cycle, that is, in the "instruction execution" phase.In terms of space, if the extracted code is an instruction, it must be sent toInstruction registerIf the extracted code is data, it must be sent toArithmetic unit。It can be seen that time control is too important for computers.
In short, the coordinated action of the computer needs a time mark, and the time mark isSequential signalTo reflect.Hardwired controllerThe main state period beat potential beat pulse three-level system is often used for timing signals in.stayMicroprogram controllerIn, the timing signal is relatively simple, generally using the beat potential beat pulse two-level system.[1]
Composition of timing generator
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The timing signal generator used in the microprogram controller is composed ofClock source, annular pulse generator, beat pulse andRead write timingdecodingLogic, start stop control logic, etc.The clock source is used as a ringPulse generatorProvide square wave with stable frequency and level matchingClock pulse signal。It is usuallyQuartz crystal oscillatorAnd a positive feedback oscillation circuit composed of NAND gate, and its output is sent to the ring pulse generator.The function of the ring pulse generator is to produce a group of orderlyintervalEqual or unequal pulse sequences to passdecodingCircuit to generate the last required beat pulse.In order to avoid interference burr on the beat pulse, the ring pulse generator usually uses a cycleshift registerForm.A typical ring pulse generator and its decoding logic adopt the form of cyclic shift register.[2]
Application of timing generator
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Used to test the system
The principle, structure and working process of each functional module of the test system based on vector testing method.Based on years of practical test experience and reference to similar test systems abroad, relevant technicians have successfully developed a test system with low production cost and reliable performance, which is suitable for the actual production situation of the domestic semiconductor industry. With the increasingly extensive application of digital integrated circuits and national support for the development of the semiconductor industry,The design capability of digital integrated circuits in China has been greatly developed.However, in general, (the design company will not consider the development of production line equipment, and most of the processing plants do not have system research and development capabilities. Therefore, most of the testing equipment used by domestic enterprises engaged in subsequent processing of integrated circuits are imported from abroad. These equipment are expensive and complex to operate, which increases the cost of integrated circuit production to a certain extent.In order to get rid of the high cost investment of equipment purchase in integrated circuit production, we have developed integrated circuit test equipment, achieved certain results, and accumulated rich experience in test technology.
For chip development
Digital logic circuits can be divided intoSequential logic circuitandCombinational logic circuit。The output of the radio band of the combined logic circuit is only related to the current input, such as NAND gate, adder, multiplier, comparatorMultiplexer, radio band encoder, decoder, etc. SET often occurs in combination logic circuit.It is related to the transistor structure of the NAND gate and the previous state of the true value radio frequency band table. For common radio frequency bands such as counters, registers, triggers, etc., SEU often occurs in sequential logic circuits.The storage unit of radio frequency band in digital circuit, such as latch and registerSRAM(Static output O is only determined by the state of input A and B, and the output of sequential logic circuit is not only related to the current input, but also related to the circuit RandomAccess Memory, radio band SRAM) The inverter feedback structure is often used to realize data storage, radio band.An ordinary unreinforced latch structure.The radio frequency band can be added at the design level (RHBD). By reasonably evaluating the radio frequency band estimation and using the system level, circuit level and other reinforcement schemes, the radio frequency band can be added with chips with reinforcement capability based on commercial manufacturing processes or full custom processes.
For integrated circuits
The integrated circuits applied in the space environment are subject toHigh-energy particleWhen bombarded by, it will ionize its oxide layer, including the radio frequency band, including the gate oxide layer or the shallow trench isolation oxide layer, and will also produce the boundary radio frequency band surface state on the contact surface of silicon and the gate oxide layer, which will lead to the drift of threshold and transmission delay, the increase of static current, and the internal leakage of the device and other damage to the radio frequency band array, and in serious cases, the device will fail.We call this effect of ionized radio band charge caused by high-energy particle bombardment, which eventually leads to device performance degradation or even failure, Total Ionizing Dose (radio band TID).Radio band When a forward bias voltage is applied to the gate of MOS tube,The physical process of MOS tube being bombarded by high-energy particles and finally introducing positive charges into the gate oxide in the radio band mainly includes the following steps: first, when the high-energy particles hit the gate oxide, their energy will be transferred to the gate oxide linearly until the energy of the particles consumes the radio band as much as possible.At the same time, a large number of electron hole pairs will be generated along the trajectory of particles, and more electron hole pairs will be ionized by particles with higher energy in the radio frequency band.After a large number of electron hole pairs are generated, most of the ionized radio band hole pairs will recombine.The recombination time is very short, usually less than 0.1ps.The number of composite electron hole radio frequency band hole pairs depends on the concentration of electron hole pairs and the size of the applied voltage.[3]
