Electronic engineer refers to all kinds of electronic equipment and information systems research, teaching, product design, technology development, production and management of senior engineering and technical personnel. Generally divided into hardware engineers and software engineers.
Hardware engineers： mainly responsible for circuit analysis, design; and computer software as a tool for PCB design, to be completed after the PCB factory and welding electronic components after the test, debugging;
Software Engineer：mainly responsible for single-chip, DSP, ARM, FPGA and other embedded program preparation and debugging. FPGA programs are sometimes a workplace for hardware engineers.
Error 1：
These pull high / low resistance to the resistance of how much resistance is not, choose an integer 5K it.
Comments: the market does not exist 5K resistance, the closest is 4.99K (accuracy 1%), followed by 5.1K (accuracy of 5%), the cost of 20% accuracy than the 4.7K 4 times and 2 times The 20% of the resistance of the resistance is only 1,1.5,2.2, 3.3,4.7,6.8 several categories (including an integer multiple of 10); Similarly, 20% of the capacitor capacitance is only the above values, if the election of the other Value must use a higher precision, the cost turned several times, but can not bring any benefits.
Error 2：
This part of the circuit as long as the requirements of the software design will not be a problem.
Comments: a lot of electrical characteristics on the hardware directly under the control of the software, but the software is often an accident, the program can not be expected after running what will be running. The designer should ensure that no matter what kind of operating hardware the software does not have permanent damage in a short period of time.
Error 3：
This logic with 74XX door circuit is also OK, but too soil, or CPLD bars, it seems more high-end.
Comments: 74XX door only a few cents, and CPLD at least have dozens of pieces. Cost increased N times do not say, back to the production, documentation and other work to add several times the work.
Error 4：
This board of PCB design requirements are not high, with a little fine line, automatic cloth it.
Comments: automatic wiring is bound to take up a larger PCB area, while producing more than a few times the manual wiring through the hole, in a large batch of products, PCB manufacturers to consider the factors in addition to factors in addition to business factors, is the line width and The number of holes, which were affected by the PCB yield and the number of drill bit consumption, saving the cost of the supplier, also gave the price to find a reason.
Error 5：
Our system is 220V power supply, do not care about power consumption.
Comments: low-power design is not just to save power, more benefits is to reduce the cost of power modules and cooling systems, due to the reduction of current also reduces the electromagnetic radiation and thermal noise interference. As the temperature of the device decreases, the life of the device is extended accordingly (the operating temperature of the semiconductor device is increased by 10 degrees and the lifetime is reduced by half).
Error 6：
These bus signals are pulled with resistance, feel more rest assured.
Comments: the signal needs to pull down a lot of reasons, but not all have to pull. Pull-down resistor pull a simple input signal, the current will be several tens of microamps below, but pull a driven signal, the current will reach the mA level, the current system is often the address data of 32, there may be 244/245 after the isolation of the bus and other signals, are pulled up, then a few watts of power consumption on these resistors (do not use 8 cents once the concept of electricity to treat this a few watts of power consumption).
Error 7：
CPU and FPGA of these unused I / O mouth how to deal with it? Let it empty it, later say.
Comments: do not have the I / O port if floating, then a little bit of interference by the outside may become a repeated oscillation of the input signal, and MOS device power depends on the number of flip the door circuit. If it pulls it up, each pin will have a microampere level current, so the best way is to set the output (of course, can not be connected to other outside the drive signal).
Error 8：
This FPGA left so many doors with endless, you can enjoy it.
Comments: FGPA power consumption and the number of flip-flops used and the number of flip is proportional to the same type of FPGA in different circuits at different times the power consumption may be a difference of 100 times. Minimizing the number of flip flops at high speed is the fundamental way to reduce FPGA power consumption.
Error 9：
The power consumption of these small chips are very low, do not consider.
Comments: For the internal less complex chip power is difficult to determine, it is mainly determined by the current on the pin, an ABT16244, no load, then the power consumption of less than 1 mA, but its indicators are each foot Can drive 60 mA load (such as matching tens of ohms resistance), that is, the maximum power consumption of up to 60 * 16 = 960mA, of course, only the power supply current is so big, the heat fell on the load.
Error 10：
Memory, there are so many control signals, I only need to use this board OE and WE signal can be, and chip to ground it, so read the data when the operation came much faster.
Comments: Most of the memory power consumption in the chip selection is valid (regardless of OE and WE how) will be more than 100 times more than the film selection is invalid, so should use CS as much as possible to control the chip, and meet other requirements to do so May shorten the width of the chip select pulse.
Error 11：
How can these signals have overshoot ah? As long as the match is good, you can eliminate the.
Comments: In addition to a few specific signals (such as 100BASE-T, CML), are overshoot, as long as not very large, do not necessarily need to match, even if the match is not to match the best. Like the TTL output impedance of less than 50 ohms, and some even 20 ohms, if also with such a large matching resistance, then the current is very large, power consumption is unacceptable, the other signal amplitude will be small can not be used, Besides the general signal output high and output low when the output impedance is not the same, but also way to achieve perfect match. So, TTL, LVDS, 422 and other signal matching as long as the overshoot can be accepted.
Error 12：
Reduce power consumption is the hardware staff, and software does not matter.
Comments: the hardware is just take a stage, singing is the software, the bus almost every chip access, each signal flipped almost by the software control, if the software can reduce the number of external access (more use of register variables, The use of internal CACHE, etc.), timely response to interrupt (interrupt is often active low and with a pull-up resistor) and other specific measures against the specific board will reduce the power to make a great contribution.
Error 13：
This clock can only handle 100M CPU 70%, for 200M frequency on the normal.
Comments: the system's handling capacity involves a variety of factors, in the communications business in the bottleneck are generally in the memory, CPU and then fast, external access is not fast is futile.
Error 14：
CPU with a little CACHE, it should be faster.
Comments: CACHE increase, does not necessarily lead to improved system performance, in some cases, but the use of CACHE close faster than the use of CACHE. The reason is that the data moved to CACHE must be reused many times to improve system efficiency. So in the communication system generally only open the instruction CACHE, data CACHE even if the opening is also limited to part of the storage space, such as the stack part. But also requires the program to take into account the CACHE capacity and block size, which involves the key code loop body length and jump range, if a cycle just a little bit more than CACHE, and in the repeated cycle, then it is miserable.
Error 15：
A CPU processing, however, with two distribution processing, processing capacity can be doubled.
Comments: For moving bricks, two people should be twice as efficient as one person; for painting, more than one person can only help. Use a few CPU need to have more understanding of the business before they can be Amotech determined to minimize the cost of coordination between the two CPUs, so that 1 +1 as close as possible, do not be less than 1.
Error 16：
This CPU with DMA module, use it to move data certainly fast.
Comments: the real DMA is the hardware to seize the bus at the same time start both ends of the device, in a cycle to read here, there some. But a lot of embedded CPU DMA is only analog, start every time before DMA to do a lot of preparatory work (set the starting address and length, etc.), the transmission is often read first in the chip temporary, and then write out, That is, to move a data to be two clock cycles, faster than the software to move (do not need to take instructions, no loop jump and other additional work), but if only a few bytes at a time, but also do a bunch of preparatory work, Generally also involves the function call, the efficiency is not high. So this DMA only applies to large data blocks.
Error 17：
To ensure a clean power supply, even the capacitor is the more the better.
Comments: In general, the more power to the capacitor, of course, will be more stable, but too many also have adverse factors: a waste of costs, wiring difficulties, power shock current is too large. To the capacitance of the design of the key is to choose the capacity and put on the place, the general chip manual have to fight even the design of the capacitor reference, the best manual to do.
Error 18：
User operation error can not blame me.
Comments: require users to strictly follow the manual operation is right, but the user is a person, there is a mistake, can not say that a mistake on the wrong machine, plug the wrong plug on the board. So the user may make a variety of mistakes must be protected.
Error 19：
The following are the same as the "This board is bad because the board side of the problem, nor is my responsibility. The following are the same as the ".
Comments: for a variety of external hardware interface should be sufficient compatibility, not because the other side of the signal is not normal, you will be a break. It should not normally affect the part of the function associated with it, and other functions should be able to work properly, should not be a thorough strike, or even permanent damage, and once the interface is restored, you should immediately return to normal. The
Error 20：
Our system requires so high, including MEM, CPU, FPGA and all other chips should choose the fastest.
Hardware engineers： mainly responsible for circuit analysis, design; and computer software as a tool for PCB design, to be completed after the PCB factory and welding electronic components after the test, debugging;
Software Engineer：mainly responsible for single-chip, DSP, ARM, FPGA and other embedded program preparation and debugging. FPGA programs are sometimes a workplace for hardware engineers.
Error 1：
These pull high / low resistance to the resistance of how much resistance is not, choose an integer 5K it.
Comments: the market does not exist 5K resistance, the closest is 4.99K (accuracy 1%), followed by 5.1K (accuracy of 5%), the cost of 20% accuracy than the 4.7K 4 times and 2 times The 20% of the resistance of the resistance is only 1,1.5,2.2, 3.3,4.7,6.8 several categories (including an integer multiple of 10); Similarly, 20% of the capacitor capacitance is only the above values, if the election of the other Value must use a higher precision, the cost turned several times, but can not bring any benefits.
Error 2：
This part of the circuit as long as the requirements of the software design will not be a problem.
Comments: a lot of electrical characteristics on the hardware directly under the control of the software, but the software is often an accident, the program can not be expected after running what will be running. The designer should ensure that no matter what kind of operating hardware the software does not have permanent damage in a short period of time.
Error 3：
This logic with 74XX door circuit is also OK, but too soil, or CPLD bars, it seems more high-end.
Comments: 74XX door only a few cents, and CPLD at least have dozens of pieces. Cost increased N times do not say, back to the production, documentation and other work to add several times the work.
Error 4：
This board of PCB design requirements are not high, with a little fine line, automatic cloth it.
Comments: automatic wiring is bound to take up a larger PCB area, while producing more than a few times the manual wiring through the hole, in a large batch of products, PCB manufacturers to consider the factors in addition to factors in addition to business factors, is the line width and The number of holes, which were affected by the PCB yield and the number of drill bit consumption, saving the cost of the supplier, also gave the price to find a reason.
Error 5：
Our system is 220V power supply, do not care about power consumption.
Comments: low-power design is not just to save power, more benefits is to reduce the cost of power modules and cooling systems, due to the reduction of current also reduces the electromagnetic radiation and thermal noise interference. As the temperature of the device decreases, the life of the device is extended accordingly (the operating temperature of the semiconductor device is increased by 10 degrees and the lifetime is reduced by half).
Error 6：
These bus signals are pulled with resistance, feel more rest assured.
Comments: the signal needs to pull down a lot of reasons, but not all have to pull. Pull-down resistor pull a simple input signal, the current will be several tens of microamps below, but pull a driven signal, the current will reach the mA level, the current system is often the address data of 32, there may be 244/245 after the isolation of the bus and other signals, are pulled up, then a few watts of power consumption on these resistors (do not use 8 cents once the concept of electricity to treat this a few watts of power consumption).
Error 7：
CPU and FPGA of these unused I / O mouth how to deal with it? Let it empty it, later say.
Comments: do not have the I / O port if floating, then a little bit of interference by the outside may become a repeated oscillation of the input signal, and MOS device power depends on the number of flip the door circuit. If it pulls it up, each pin will have a microampere level current, so the best way is to set the output (of course, can not be connected to other outside the drive signal).
Error 8：
This FPGA left so many doors with endless, you can enjoy it.
Comments: FGPA power consumption and the number of flip-flops used and the number of flip is proportional to the same type of FPGA in different circuits at different times the power consumption may be a difference of 100 times. Minimizing the number of flip flops at high speed is the fundamental way to reduce FPGA power consumption.
Error 9：
The power consumption of these small chips are very low, do not consider.
Comments: For the internal less complex chip power is difficult to determine, it is mainly determined by the current on the pin, an ABT16244, no load, then the power consumption of less than 1 mA, but its indicators are each foot Can drive 60 mA load (such as matching tens of ohms resistance), that is, the maximum power consumption of up to 60 * 16 = 960mA, of course, only the power supply current is so big, the heat fell on the load.
Error 10：
Memory, there are so many control signals, I only need to use this board OE and WE signal can be, and chip to ground it, so read the data when the operation came much faster.
Comments: Most of the memory power consumption in the chip selection is valid (regardless of OE and WE how) will be more than 100 times more than the film selection is invalid, so should use CS as much as possible to control the chip, and meet other requirements to do so May shorten the width of the chip select pulse.
Error 11：
How can these signals have overshoot ah? As long as the match is good, you can eliminate the.
Comments: In addition to a few specific signals (such as 100BASE-T, CML), are overshoot, as long as not very large, do not necessarily need to match, even if the match is not to match the best. Like the TTL output impedance of less than 50 ohms, and some even 20 ohms, if also with such a large matching resistance, then the current is very large, power consumption is unacceptable, the other signal amplitude will be small can not be used, Besides the general signal output high and output low when the output impedance is not the same, but also way to achieve perfect match. So, TTL, LVDS, 422 and other signal matching as long as the overshoot can be accepted.
Error 12：
Reduce power consumption is the hardware staff, and software does not matter.
Comments: the hardware is just take a stage, singing is the software, the bus almost every chip access, each signal flipped almost by the software control, if the software can reduce the number of external access (more use of register variables, The use of internal CACHE, etc.), timely response to interrupt (interrupt is often active low and with a pull-up resistor) and other specific measures against the specific board will reduce the power to make a great contribution.
Error 13：
This clock can only handle 100M CPU 70%, for 200M frequency on the normal.
Comments: the system's handling capacity involves a variety of factors, in the communications business in the bottleneck are generally in the memory, CPU and then fast, external access is not fast is futile.
Error 14：
CPU with a little CACHE, it should be faster.
Comments: CACHE increase, does not necessarily lead to improved system performance, in some cases, but the use of CACHE close faster than the use of CACHE. The reason is that the data moved to CACHE must be reused many times to improve system efficiency. So in the communication system generally only open the instruction CACHE, data CACHE even if the opening is also limited to part of the storage space, such as the stack part. But also requires the program to take into account the CACHE capacity and block size, which involves the key code loop body length and jump range, if a cycle just a little bit more than CACHE, and in the repeated cycle, then it is miserable.
Error 15：
A CPU processing, however, with two distribution processing, processing capacity can be doubled.
Comments: For moving bricks, two people should be twice as efficient as one person; for painting, more than one person can only help. Use a few CPU need to have more understanding of the business before they can be Amotech determined to minimize the cost of coordination between the two CPUs, so that 1 +1 as close as possible, do not be less than 1.
Error 16：
This CPU with DMA module, use it to move data certainly fast.
Comments: the real DMA is the hardware to seize the bus at the same time start both ends of the device, in a cycle to read here, there some. But a lot of embedded CPU DMA is only analog, start every time before DMA to do a lot of preparatory work (set the starting address and length, etc.), the transmission is often read first in the chip temporary, and then write out, That is, to move a data to be two clock cycles, faster than the software to move (do not need to take instructions, no loop jump and other additional work), but if only a few bytes at a time, but also do a bunch of preparatory work, Generally also involves the function call, the efficiency is not high. So this DMA only applies to large data blocks.
Error 17：
To ensure a clean power supply, even the capacitor is the more the better.
Comments: In general, the more power to the capacitor, of course, will be more stable, but too many also have adverse factors: a waste of costs, wiring difficulties, power shock current is too large. To the capacitance of the design of the key is to choose the capacity and put on the place, the general chip manual have to fight even the design of the capacitor reference, the best manual to do.
Error 18：
User operation error can not blame me.
Comments: require users to strictly follow the manual operation is right, but the user is a person, there is a mistake, can not say that a mistake on the wrong machine, plug the wrong plug on the board. So the user may make a variety of mistakes must be protected.
Error 19：
The following are the same as the "This board is bad because the board side of the problem, nor is my responsibility. The following are the same as the ".
Comments: for a variety of external hardware interface should be sufficient compatibility, not because the other side of the signal is not normal, you will be a break. It should not normally affect the part of the function associated with it, and other functions should be able to work properly, should not be a thorough strike, or even permanent damage, and once the interface is restored, you should immediately return to normal. The
Error 20：
Our system requires so high, including MEM, CPU, FPGA and all other chips should choose the fastest.
Comments: In a high-speed system is not every part of the work in the high-speed state, and the device speed for each increase in a level, the price is almost doubled, and also give the signal integrity problem has a great negative impact.
