Microcontroller
 
   
 
Q1 :  What are the connections between R0 and R4?
Q2 :  What is the difference between RET and RETI?
Q3 :  Are all the MCU has the same reset address which is 0000H?
Q4 :  Is there interrupt priority in MCU? Can it be nested ?
Q5 :  What’s the shortest time required for the AD sampling time ?
Q6 :  What is the value of pull-low resistance in EM78P156E?
Q7 :  What are the differences between the OTP and the FLASH tools for programming?
Q8 :  What is the frequency of the IRC in ICE?
Q9 :  How to deal with the unused I/O pin?
Q10 :  How many instructions in one page at most?
Q11 :  How to calculate the instruction time?
Q12 :  How to calculate the WDT time out?
Q13 :  What are the differences between the commercial grade MCU and industrial grade MCU ?
Q14 :  When will the open-drain be used for I/O?


  Answer
Q1 :   What are the connections between R0 and R4?
  When using the indirect address, we put the RAM ADDRESS into R4 first, then we can W/R RAM through R0.

Example

MOV A,@0X10

MOV 0X10,A

LOOP:        MOV A,@0X20

MOV R4,A

CLRA

MOV R0,A

INC R4

DJZ 0X10

JMP LOOP

 




Q2 :   What is the difference between RET and RETI?
  RET is the instruction to be used when program returns from the called subprogram. RETI is the instruction to be used when program returns from Interrupt routine.


Q3 :   Are all the MCU has the same reset address which is 0000H?
  No, some MCU are different, for example the reset address for the EM78P447 is 0XFFF.


Q4 :   Is there interrupt priority in MCU? Can it be nested ?
  Some MCU interrupt are with the priority structure, some not. We can know from the data sheet. Interrupt cannot be nested.


Q5 :   What’s the shortest time required for the AD sampling time ?
  It usually needs more than 4 TAD


Q6 :   What is the value of pull-low resistance in EM78P156E?
  About 71K ohm.


Q7 :   What are the differences between the OTP and the FLASH tools for programming?
  We should use DWETR to write OTP and use FWTR to write FLASH


Q8 :   What is the frequency of the IRC in ICE?
  The IRC frequency of ICE is 4M Hz.


Q9 :   How to deal with the unused I/O pin?
  The unused pin shall be set as output pin. If unused I/O pins are floating, the IC will consume more power.


Q10 :   How many instructions in one page at most?
  One program page is 1024 instructions.


Q11 :   How to calculate the instruction time?
  When we set the CLKS to 0,the single instruction time is 2/system frequency. When we set the CLKS to 1,the single instruction time is 4/system frequency.


Q12 :   How to calculate the WDT time out?
  18MS* prescaler。Note: The 18MS will be changed by the work-voltage and temperature.


Q13 :   What are the differences between the commercial grade MCU and industrial grade MCU ?
  a. The industrial grade MCU is stronger for noise immunity b. The industrial grade MCU can work under the worse surroundings than the commercial grade for wider temperature range than the commercial c. The commercial grade can work on lower voltage than the industrial grade.


Q14 :   When will the open-drain be used for I/O?
  When two different power systems need to communicate with each other.