USCI Operation: UART Mode
19-7
Universal Serial Communication Interface, UART Mode
The UCDORM bit is used to control data reception in the idle-line
multiprocessor format. When UCDORM = 1, all non-address characters are
assembled but not transferred into the UCAxRXBUF, and interrupts are not
generated. When an address character is received, the character is
transferred into UCAxRXBUF, UCAxRXIFG is set, and any applicable error
flag is set when UCRXEIE = 1. When UCRXEIE = 0 and an address character
is received but has a framing error or parity error, the character is not
transferred into UCAxRXBUF and UCAxRXIFG is not set.
If an address is received, user software can validate the address and must
reset UCDORM to continue receiving data. If UCDORM remains set, only
address characters will be received. When UCDORM is cleared during the
reception of a character the receive interrupt flag will be set after the reception
completed. The UCDORM bit is not modified by the USCI hardware
automatically.
For address transmission in idle-line multiprocessor format, a precise idle
period can be generated by the USCI to generate address character identifiers
on UCAxTXD. The double-buffered UCTXADDR flag indicates if the next
character loaded into UCAxTXBUF is preceded by an idle line of 11 bits.
UCTXADDR is automatically cleared when the start bit is generated.
Transmitting an Idle Frame
The following procedure sends out an idle frame to indicate an address
character followed by associated data:
1) Set UCTXADDR, then write the address character to UCAxTXBUF.
UCAxTXBUF must be ready for new data (UCAxTXIFG = 1).
This generates an idle period of exactly 11 bits followed by the address
character. UCTXADDR is reset automatically when the address character
is transferred from UCAxTXBUF into the shift register.
2) Write desired data characters to UCAxTXBUF. UCAxTXBUF must be
ready for new data (UCAxTXIFG = 1).
The data written to UCAxTXBUF is transferred to the shift register and
transmitted as soon as the shift register is ready for new data.
The idle-line time must not be exceeded between address and data
transmission or between data transmissions. Otherwise, the transmitted
data will be misinterpreted as an address.
Содержание MSP430x4xx Family
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