Datasheet

Table Of Contents
Section 13 Serial Communication Interface
REJ09B0140-0900 Rev. 9.00 Page 459 of 846
Sep 16, 2010
H8S/2215 Group
13.8 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 13.37 shows an example of
communication using the SCI select function. Figure 13.38 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.
Interrupt
controller
TSR0_ARSR0_A
Transmission/
reception
control
Slave LSI_A (This LSI)Master LSI
SCK0_A
SCK0_B
C/A = CKE1 = SSE = 1
Slave LSI_B (This LSI)
SEL_A
IRQ7_A
IRQ7_BSEL_B
M_TxD
RxD0_A
TxD0_A
RxD0_B
TxD0_B
SCK0
SCK0
M_RxD
M_SCK
Figure 13.37 Example of Communication Using the SCI Select Function