Microfriend DYNA-85 is an introduction to a low cost trainer and development kit. It was developed to assist the novice to get familiar with INTEL 8085 microprocessor in a user friendly environment.
There are two parts of this project.
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The stopwatch displayed time in minutes, seconds and 1/100th of a second format.
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We need a delay of 10 ms for the 1/100th second values, so we wrote a routine to implement that.
LXI D,04E2
UP : DCX D
MOV A,D
ORA E
JNZ UPThis routine ensures that we get a delay of 10ms.
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The data field of the display shows 1/100th second value while address field shows the minutes and seconds value. When the data field value reaches 63H (or 100), we need to update seconds while making data field zero.
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When the seconds field reaches 59, we need to update the minutes field and make seconds zero.
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when the stopwatch reaches 59:59:99 , we just jump back to the beginning (i.e. 00:00:00).
- For achieving this part, we used vector interrupt(VI) on the machine which is basically the RST 7.5 of 8085 microprocesser.
- We kept the value of B register as 00H for most of the time when the stopwatch code runs.
- When we press VI for the first time, stopwatch goes to PAUSE mode while value of B register is updated to 01H. We achieve this mode by running the interrupt code into an infinite loop.
- When we press VI for the second time , this is the RESET mode, where value of B register is 01H, so we first update the value of B register to 02H and then reset A register to 00H and HL register pair to 0000H and run that in an infinite loop.
- When we press VI for the third time, this is the START mode, where we just return to the stopwatch routine and thus, continue the flow of the stopwatch code and value of B register goes back to 00H.
This project was made by
Srijan Sankrit (https://github.com/SrijanSankrit) - Team Leader
Sarvesh Choushetti (https://github.com/choushetti)