TMPM330 - Keil

Transmit Buffer
Under development
TMPM330 (rev 0.4) 9-20
TMPM330
The transmit buffer (SC0BUF) is in a dual structure. The double buffering function may be
enabled or disabled by setting the double buffer control bit in serial mode control
register 2 (SC0MOD2). If double buffering is enabled, data written to Transmit Buffer 2
(SCOBUF) is moved to Transmit Buffer 1 (shift register).
If the transmit FIFO has been disabled (SCOFCNF = 0 or 1 and SC0MOD1<
FDPX1:0>=01), the INTTX0 interrupt is generated at the same time and the transmit
buffer empty flag of SC0MOD2 is set to “1.” This flag indicates that Transmit
Buffer 2 is now empty and that the next transmit data can be written. When the next data is
written to Transmit Buffer 2, the flag is cleared to “0.”
If the transmit FIFO has been enabled (SCNFCNF = 1 and SC0MOD1=10/11), any data in the transmit FIFO is moved to the Transmit Buffer 2 and
flag is immediately cleared to “0.” The CPU writes data to Transmit Buffer 2 or to the
transmit FIFO.
If the transmit FIFO is disabled in the I/O interface SCLK input mode and if no data is set in
Transmit Buffer 2 before the next frame clock input, which occurs upon completion of data
transmission from Transmit Buffer 1, an under-run error occurs and a serial control register
(SC0CR) parity/under-run flag is set.
If the transmit FIFO is enabled in the I/O interface SCLK input mode, when data
transmission from Transmit Buffer 1 is completed, the Transmit Buffer 2 data is moved to
Transmit Buffer 1 and any data in transmit FIFO is moved to Transmit Buffer 2 at the same
time.
If the transmit FIFO is disabled in the I/O interface SCLK output mode, when data in
Transmit Buffer 2 is moved to Transmit Buffer 1 and the data transmission is completed, the
SCLK output stops. So, no under-run errors can be generated.
If the transmit FIFO is enabled in the I/O interface SCLK output mode, the SCLK output
stops upon completion of data transmission from Transmit Buffer 1 if there is no valid data
in the transmit FIFO.
Note) In the I/O interface SCLK output mode, the SC0CR flag is
insignificant. In this case, the operation is undefined. Therefore, to switch
from the SCLK output mode to another mode, SC0CR must be read in
advance to initialize the flag.
If double buffering is disabled, the CPU writes data only to Transmit Buffer 1 and the
transmit interrupt INTTX0 is generated upon completion of data transmission.
If handshaking with the other side is necessary, set the double buffer control bit to
“0” (disable) to disable Transmit Buffer 2; any setting for the transmit FIFO should not be
performed.
Serial Channel (SIO)