SLAU846A June 2023 – October 2023 MSPM0G1105 , MSPM0G1106 , MSPM0G1107 , MSPM0G1505 , MSPM0G1506 , MSPM0G1507 , MSPM0G3105 , MSPM0G3105-Q1 , MSPM0G3106 , MSPM0G3106-Q1 , MSPM0G3107 , MSPM0G3107-Q1 , MSPM0G3505 , MSPM0G3505-Q1 , MSPM0G3506 , MSPM0G3506-Q1 , MSPM0G3507 , MSPM0G3507-Q1
When IDLELINE is set in the CTL0.MODE register bits, the idle-line multiprocessor format is selected. Blocks of data are separated by an idle time on the transmit or receive lines (Figure 16-10). An idle receive line is detected when ten or more continuous ones (marks) are received after the one or two stop bits of a character. The baud-rate generator is switched off after reception of an idle line until the next start edge is detected. When an idle line is detected, the IDLE bit in UARTx.STAT is set. In Idle-Line mode the UART receiver operates in no parity mode and the UART word length (UARTx.LCRH.WLEN) must be set to 8bit.
The first character received after an idle period is an address character. The IDLE bit in UARTx.STAT register is used as an address tag for each block of characters. In idle-line multiprocessor format, this bit is set when a received character is an address.
If an address character is received it is compared against the ADDR register with the AMASK applied. If the received character matches, the address character and all following received characters are transferred into the RXDATA buffer and interrupts/flags are generated until the next address without a match is received. The IDLE bit in UARTx.STAT register is automatically cleared when the address does match; otherwise the IDLE bit is set until the address is matched.
When the SENDIDLE bit in UARTx.LCRH register is set the UART inserts an idle period of 11 bit times on the bus, an ongoing transfer is finished first. The next transfer will be delayed till this idle period has finished. Then the next transfer can start with an address character.
The following procedure sends out an idle frame to indicate an address character followed by associated data:
The idle-line time must not be exceeded between address and data transmission or between data transmissions. Otherwise, the transmitted data is misinterpreted as an address.
BUSY bit in IDLELINE mode: