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16.6.5
Simultaneous Serial Data Transmission and Reception (Clocked Synchronous
Mode)
Figure 16.23 shows a sample flowchart for simultaneous serial transmit and receive operations.
After initializing the SCI, the following procedure should be used for simultaneous serial data
transmit and receive operations. To switch from transmit mode to simultaneous transmit and
receive mode, after checking that the SCI has finished transmission and the TDRE and TEND
flags in SSR are set to 1, clear the TE bit in SCR to 0. Then simultaneously set the TE and RE bits
to 1 with a single instruction. To switch from receive mode to simultaneous transmit and receive
mode, after checking that the SCI has finished reception, clear the RE bit to 0. Then after checking
that the RDRF bit in SSR and receive error flags (ORER, FER, and PER) are cleared to 0,
simultaneously set the TE and RE bits to 1 with a single instruction.
16.6.6
SCI Selection in Serial Enhanced Mode
SCI_0 and SCI_2 provides the following capability according to the serial enhanced mode
registers (SEMR_0 and SEMR_2) settings.
If the SCI is used in clocked synchronous mode with clock input, the SCI channel can be
enabled/disabled using the input at the external pins. The external pins include PA0/SSE0I
(SCI_0) and PA1/SSE2I (SCI_2); therefore, this capability is not available in modes where the
PA0 and PA1 pins are automatically set for address output.
When the SCI operation is disabled (not selected) by input at the external pins, TxD output is fixed
to the high-impedance state and SCK input is internally fixed to high. One-to-multipoint
communication is possible if the master device, which outputs SCK, controls these external pins
for chip selection. SCI selection capability is selected using the SSE bits in SEMR.
Section 16 Serial Communication Interface (SCI, IrDA, and CRC)
Rev. 3.00 Jan 25, 2006 page 443 of 872
REJ09B0286-0300
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