Foreword
Accompanying the development with electronic rapid technology, more and more people join the main force that the electron develops. In the process that studies electronic technology and project of research and development, cannot avoid to want to use a few instruments, for example avometer, oscillograph is waited a moment, however professional to a few blame lover, having oscillograph of a number is to compare " extravagant " . Design digital oscillograph of the introduction originally, because its have cost low, make simple, measure precision advanced advantage, just satisfied the requirement of person of this one part.
Make an oscillograph simple, but the oscillograph that wants to make tall imitate input bandwidth is not easy however. The choice of main parts of an apparatus is the key that realizes tall imitate to input bandwidth to design an object. The article chooses C8051F020 sheet piece machine as CPU, it has simple 51 kernels and I ／ O is resourceful. A ／ D chooses ／ of model of 8 high speed to count converter TDA8703, highest sampling rate is 40 Msps. Additional, use double mouth FIFO-IDT7202LA-12, it is memory of first-in first-out double mouth, the fastest stock time to be 12 Ns.
This system basically includes circuit of front imitate signal to recuperate module, signal to collect circuit module, signal to transmit logic of module, each chip to control circuit module, indication module to wait.

Circuit of signal of 1 front imitate recuperates module
This module uses high speed carry to put AD744 of LM6361 and high speed comparator, if pursue,1 is shown.

This design chooses finished product probe. Press an input to had prevented, in high speed comparator AD744 front adds 2 protection diode, embed input signal arrive inside ± 12 V, to action is being protected since whole system. Magnify reversely through ICI next, again classics IC2 phasic answer signal starting phase. The range of AD voltage input that because be designed originally,uses is 1. 55 ～ 3. 26 V, so applied IC3 adds weight of a dc input signal " carry " inside the input limits of A ／ D.

2 signal collect circuit module
The converter of A ／ D that this module uses is TDA8703. The ／ of high speed model that it is Philips company production counts converter, sampling rate is 40 Msps, 8 resolution, letter a confusion of voices is compared very tall, as compatible as TTL n, have in-house and referenced voltage.
If the input voltage of TDA8703 and output binary code express a kind, sampling sequential is shown 2 times like the graph.

The ascendant edge of clock begins sampling when arrival, when the next cycle of clock ascendant edge rises when, changeover ends. Because be as high as the sampling rate of 40 Msps, common sheet piece machine is very difficult can " catch up with rhythm " , use double mouth RAM at this moment -- IDT7202, cooperate to use to it, in order to achieve with sheet piece the purpose of machine synchronism. IDT7202 is a when AMD company rolls out advanced ／ gives double mouth memory first. The model that this design chooses is IDT7202-12, the time that stocks data namely is 12 Ns, stock frequency to be as high as 83 MHz namely, can match completely with the AD of 40 Msps, so two chip can use same clock sampling and store (if pursue,3 show) . IDT7202 has the memory depth of 1 024 byte, low power comsumption, CMOS craft, 3 kinds of condition indicate (empty, half full, full) , industrial level temperature (80 ℃ of one 40 ～ ) .
Previous12 Next