4524_M Datasheet, PDF (226/310 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 720 FAMILY / 4500 SERIES

4524 Group
APPLICATION
2.5 Serial I/O
(2) Transmit/receive operation of slave
➀ Set the transmit data into the serial I/O register SI with the TSIAB instruction.
When the TSIAB instruction is executed, the contents of register A are transferred to the low-
order bits of register SI and the contents of register B are transferred to the high-order bits of
register SI. At this time, the SCK pin must be at the “H” level.
➁ Start serial transmit/receive with the SST instruction. However, in Figure 2.5.2 where an external
clock is selected, transmit/receive is not started until the clock is input. When the SST instruction
is executed, the serial I/O transmit/receive completion flag (SIOF) is cleared to “0.”
➂ The microcomputer on the master side is informed that the receiving side is ready to receive.
In the connection example in Figure 2.5.2, the control signal “L” level is output.
➃ The transmit data is output from the SOUT pin synchronously with the falling edges of the shift
clock.
➄ The transmit data is output bit by bit beginning with the LSB of register SI. Each time one bit is
output, the contents of register SI are shifted to one bit position toward the LSB.
➅ Also, the receive data is input from the SIN pin synchronously with the rising edges of the shift
clock.
➆ The receive data is input bit by bit to the MSB of register SI.
➇ A serial I/O interrupt request occurs when the transmit/receive is completed, and the SIOF flag
is set to “1.”
➈ Read the receive data within the serial I/O interrupt service routine; or read the data after examining
the completion of the transmit/receive operation with the SNZSI instruction without using an interrupt.
Also, the SIOF flag is cleared to “0” when an interrupt occurs or the SNZSI instruction is executed.
➉ Set the control signal pin level to “H” after the receive operation is completed.
Note: Repeat steps ➀ through ➉ to transmit/receive multiple data in succession.
2.5.4 Serial I/O application example
(1) Serial I/O
Outline: The 4524 Group can communicate with peripheral ICs.
Specifications: Figure 2.5.2 Serial I/O connection example.
Figure 2.5.5 shows the setting example when a serial I/O interrupt of master side is not used, and
Figure 2.5.6 shows the slave serial I/O setting example.
Rev.2.00 Aug, 06 2004
REJ09B0107-0200Z
2-62