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[SOLVED] Circuit Expliantion Needed : OLIMEX JTAG Cable

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0by1

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Circuit Explanation Needed : OLIMEX JTAG Cable

Hi all,

I am refering OLIMEX JTAG Cable schematic for building my MSP430 programmer.
I have some doubts in that :-

1. How power is taken from parallel port data lines?
2. What is use of MCP601? can I skip this?

msp430-jtag-d-sch.gif
 

power is derived from the par port signals.
mcp601 is that one which generates Vdd.
 

MCP601 is wired as a unity gain buffer, the output voltage will be equal to the input voltage of the positive input.
When PIN4 of the jtag plug is not connected then the positive input of the opamp will have 3.3v from the output of the TSP77030 so the output of the opamp will be 3v3.
When PIN4 is connected to the voltage of the target (it seems to be an voltage sense input from the target boards) then the default 3v3 is overridden since there is a resistor of 33k and the output of the opamp will be the same as the voltage it gets from input (jtag pin4) , for example it can become 2.5v or 2v etc.

Alex
 
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    0by1

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got it :grin:
 

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