Datasheet

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28.3.4.1.2 Receiving Data in Multi-Buffer Mode
Multi-Buffer Mode is selected when MBUF MODE bit is 1. In this mode SCI/LIN sets the RXRDY bit after
receiving the programmed number of data in the receive buffer and the checksum field, the complete
frame. The error condition detection logic is same as Single Buffer mode, except that it monitors for the
complete frame. Like Single Buffer mode, you can use either Interrupt, DMA or polling method to read the
data. The received data has to be read from the LINRD0 and LINRD1 register, based on the number of
bytes. For LENGTH less than or equal to 4, Read to LINRD0 register will clear the “RXRDY” flag. For
LENGTH greater than 4, Read to LINRD1 register will clear the “RXRDY” flag. If checksum scheme is
enabled by setting CC bit during the reception of the data, then the byte that is received after the reception
of the programmed no. of data bytes indicated by LENGTH is treated as a checksum byte and compared.
28.3.4.2 Transmitting Data
The SCI transmitter is enabled if the TX FUNC bit and the TXENA bit are set to 1. If the TX FUNC bit is
not set, the LINTX pin functions as a general purpose I/O pin rather than as an SCI function pin. Any
value written to the TD0 before TXENA is set to 1 is not transmitted. Both of these control bits allow for
the SCI transmitter to be held inactive independently of the receiver.
ID TX flag is set after a valid LIN ID is received with TX Match, generated ID interrupt if enabled.
28.3.4.2.1 Transmitting Data in Single-Buffer Mode
Single Buffer Mode is selected when MBUF MODE bit is 0. In this mode LIN waits for data to be written to
TD0, transfers it to SCITXSHF, and transmits it. The flags TXRDY and TX EMPTY indicate the status of
the transmit buffers. That is, when the transmitter is ready for data to be written to TD0, the TXRDY bit is
set. Additionally, if both TD0 and SCITXSHF are empty, then the TX EMPTY bit is also set.
You can transmit data by:
1. Polling Transmit Ready Flag
2. Receive Interrupt
3. DMA
In polling method, software can poll for TXRDY bit to go high before writing the data to TD0 register. CPU
is unnecessarily overloaded by doing this Polling method. To avoid this, you can use either Interrupt or
DMA method. To use interrupt method SET TX INT bit should be set and to use DMA SET TX DMA bit
should be set. Either an Interrupt or a DMA request is generated the moment TXRDY is set. When the
SCI has completed transmission of all pending frames, the SCITXSHF register and TD0 are empty, the
TXRDY bit is set, and an interrupt/DMA request is generated, if enabled. Because all data has been
transmitted, the interrupt/DMA request should be halted. This can be done by either disabling the transmit
interrupt (CLR TX INT) / DMA request (CLR TX DMA bit) or by disabling the transmitter (clear TXENA bit).
In checksum scheme once Send Checksum SC bit is set, the checksum will be sent after the current
transmission.
NOTE: The TXRDY flag cannot be cleared by reading the corresponding interrupt offset in the
SCIINTVECT0 or SCIINTVECT1 register.
28.3.4.2.2 Transmitting Data in Multi-Buffer Mode
Multi-Buffer Mode is selected when MBUF MODE bit is 1. Similar to Single Buffer mode the software can
use polling, Interrupt or DMA method to write the data to be transmitted. The data to be transmitted has to
be written to LINTD0 and LINTD1 register, based on the number of bytes. SCI/LIN waits for data to be
written to Byte 0(TD0) of LINTD0 register and transfers the programmed number of bytes to SCITXSHF to
transmit one by one automatically. In checksum scheme once Send Checksum SC bit is set, the
checksum will be sent after transmission of programmed no. of data bytes indicated by LENGTH field.
1382
Serial Communication Interface (SCI)/Local Interconnect Network (LIN) SPNU562–May 2014
Module
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