4524_M Datasheet, PDF (225/310 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 720 FAMILY / 4500 SERIES

4524 Group
APPLICATION
2.5 Serial I/O
The full duplex communication of master and slave is described using the connection example shown in
Figure 2.5.2.
(1) Transmit/receive operation of master
➀ Set the transmit data to 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
4 bits of register SI and the contents of register B are transferred to the high-order 4 bits of register
SI.
➁ Check whether the microcomputer on the slave side is ready to transmit/receive or not.
In the connection example in Figure 2.5.2, check that the input level of control signal is “L” level.
➂ Start serial transmit/receive with the SST instruction.
When the SST instruction is executed, the serial I/O transmit/receive completion flag (SIOF) is
cleared to “0.”
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 is shifted 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 data is completed, and the SIOF
flag is set to “1.”
➈ The receive data is taken in within the serial I/O interrupt service routine; or the data is taken in
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.
Notes 1: Repeat steps ➀ through ➈ to transmit/receive multiple data in succession.
2: For the program on the master side, start to transmit the next data at the next timing
(control signal turns “L”). Do not start to transmit the next data during the previous data
transfer (control signal = “L”).
Rev.2.00 Aug, 06 2004
REJ09B0107-0200Z
2-61