Hello:
In several MCUs of the MSP430 family, during the bootstrap loader mode, the normal UART Tx/Rx transmit/pins aren't used. Instead, other pins are alloted for BSL transmit and receive.
Would you know if the normal Tx transmit output pin goes in high-impedance mode during the BSL mode?
Also, is there any register bit or pin offering information on "normal" vs "BSL" status?
Thanks.
Jerry
I've never seen an app note that discusses it. However, my understanding of BSL mode is that it is implemented as an actual MSP430 program resident in mask-ROM on the chip. This implies that unless the program specifically initializes unused pins, all I/O drivers will be in the POR state, which in almost all cases is hi-Z.
You should check this on a device specific basis with your TI FAE. But I would bet money on it.
Thank you for your posting.
This is what TI replied to our HW designer (who's using the two diodes amd a pull-up resistor to connect the two Tx outputs together, the normal one and the BSL one):
TI:
------ Your assumptions about the UTXDO and URXDO in BSL mode are correct.
------
HW designer:
------- My issue is resolved based on the assumptions that in BSL mode, always:
UTXDO is OUT in High state [he means High level, not high-impedance, here]
URXDO is IN
Should I consider these reliable assumptions?
--------
Jerry
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