Can the global register in the MAX14830 be used for a THR write?

Q: Is it possible to write to all four UART THR registers with one global command? 

A: The Global Command Register doesn't allow you to write to the THR of all 4 UARTs simultaneously. When using the global command register, the address is the global command register, and the data is one of the commands listed in table 8. You can't use it to select another address (e.g. the THR) and send data there. Its main applications are extending the address space and writing a command that can trigger transmitter synchronization.

While you can't simultaneously write the same data to each FIFO, you can use the global register and TxSynch to have all 4 FIFOs send the same data simultaneously. In order to do this, you would have to

1. Disable the 4 transmitters
2. Extend the register space
3. Enable the 4 TxSynch registers and have them trigger on the same global command
4. Disable register space extension
5. Write the data to each of the 4 UART THRs
6. Send the global command to the global command register to enable all 4 UARTs to transmit the data simultaneously.