Datasheet

Section 15 Serial Communication Interface (SCI)
Rev. 6.00 Mar. 18, 2010 Page 620 of 982
REJ09B0054-0600
15.8 SCI Select Function (H8S/2239 Group Only)
SCI_0 provides the SCI select function that enables one-to-one clocked synchronous
communication between a master LSI and multiple slave LSIs (these LSIs). Figure 15.36 shows an
example of communication using the SCI select function and figure 15.37 shows the summary of
its operation.
The master LSI enables to communicate with the slave LSI_A by setting the SEL_A signal to low
and the SEL_B signal to high. In this case, the TxD0_B pin of the slave LSI_B becomes Hi-Z and
that fixes the on-chip SCK0_B signal high, causing the communication terminated. To
communicate with the slave LSI_B, set the SEL_A signal to high and the SEL_B signal to low.*
The slave LSI detects its being selected by the low input interrupt of IRQ7 and handles data
transferring smoothly.
Note: * Change the select signal of the master LSI (SEL_A or SEL_B) while the serial clock
(M_SCK) is high after the last bit of the transmit data has been output. In addition, set
only one select signal to low at a time.
Interrupt
controller
TSR0_ARSR0_A
Transfer
control
Slave LSI_A (this LSI)Master LSI
SCK0_A
C/A = CKE1 = SSE = 1
Slave LSI_B (this LSI)
SEL_A
IRQ7
IRQ7SEL_B
M_TxD
RxD0
TxD0
RxD0
TxD0
SCK0
SCK0
M_RxD
M_SCK
Figure 15.36 Example of Communication Using SCI Select Function