We are trying to connect and use the external Voltage supervisor, TLC7733, with the MSP430F5638.
However, when we composed the circuit like this, we confirmed that the firmware loading did not work properly.
After searching for information related to this, we found that an external reset IC can interfere with communication of the JTAG interface.
Regarding this, I have seen a lot of advice not to use an external reset IC, but due to the usage environment of our product, an external reset IC must be used to ensure circuit stability.
As a solution to this, we considered connecting the external Reset IC and the reset terminal of the JTAG to the MCU's Reset port using an AND logic circuit, but there was no space to add components to the already designed PCB.
So, while looking for another solution, we accidentally found that the firmware was loaded normally when we removed the VCC pin among the JTAG connection pins (VCC, GND, RST, TEST, TCK, TMS, TDI, TDO).
Even though there is no separate power supplied to the PCB.
We tried loading the firmware several times using a total of 5 PCB samples with the VCC pin removed from the JTAG connection and confirmed that all loaded successfully.
However, we still don't know how the firmware can be loaded successfully without a VCC connection.
Can someone please explain this phenomenon to us?
Is it OK to continue loading firmware in this way?
