USCI Operation: UART Mode
19-11
Universal Serial Communication Interface, UART Mode
When a break/synch field is received, user software must reset UCDORM to
continue receiving data. If UCDORM remains set, only the character after the
next reception of a break/synch field will be received. The UCDORM bit is not
modified by the USCI hardware automatically.
When UCDORM = 0 all received characters will set the receive interrupt flag
UCAxRXIFG. If UCDORM is cleared during the reception of a character the
receive interrupt flag will be set after the reception is complete.
The counter used to detect the baud rate is limited to 07FFFh (32767) counts.
This means the minimum baud rate detectable is 488 Baud in oversampling
mode and 30 Baud in low-frequency mode.
The automatic baud rate detection mode can be used in a full-duplex
communication system with some restrictions. The USCI can not transmit data
while receiving the break/sync field and if a 0h byte with framing error is
received any data transmitted during this time gets corrupted. The latter case
can be discovered by checking the received data and the UCFE bit.
Transmitting a Break/Synch Field
The following procedure transmits a break/synch field:
1) Set UCTXBRK with UMODEx = 11.
2) Write 055h to UCAxTXBUF. UCAxTXBUF must be ready for new data
(UCAxTXIFG = 1).
This generates a break field of 13 bits followed by a break delimiter and the
synch character. The length of the break delimiter is controlled with the
UCDELIMx bits. UCTXBRK is reset automatically when the synch
character is transferred from UCAxTXBUF into the shift register.
3) 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.
Содержание MSP430x4xx Family
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