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13.7
SCI Select Function
The SCI_0 supports the SCI select function which allows clock synchronous communication
between master LSI and one of multiple slave LSI. Figure 13.24 shows an example of
communication using the SCI select function. Figure 13.25 shows the operation.
The master LSI can communicate with slave LSI_A by bringing SEL_A and SEL_B signals low
and high, respectively. In this case, the TxD0_B pin of the slave LSI_B is brought high-
impedance state and the internal SCK0_A signal is fixed high. This halts the communication
operation of slave LSI_B. The master LSI can communicate with slave LSI_B by bringing the
SEL_A and SEL_B signals high and low, respectively*.
The slave LSI detects the selection by receiving the low level input from the IRQ7 pin and
immediately executes data transmission/reception processing.
Note: * The selection signals (SEL_A and SEL_B) of the LSI must be switched while the serial
clock (M_SCK) is high after the end bit of the transmit data has been send. Note that one
selection signal can be brought low at the same time.
Rev. 3.0, 10/02, page 405 of 686
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