HD404816FS datasheet(59/100 Pages) RENESAS

59 / 100 page

HD404818 Series

Selection and Change of the Operation Mode: Table 25 shows the serial interface operation modes

which are determined by a combination of the value in the port mode register and in the serial mode

Initialize the serial interface by writing to the serial mode register to change the operation mode of the

serial interface.

Table 25 Serial Interface Operation Mode

SMR3

PMRA1

PMRA0

Serial Interface Operating Mode

Clock continuous output mode

Transmit mode

Receive mode

Transmit/receive mode

Operating State of Serial Interface: The serial interface has three operating states: the STS waiting state,

transmit clock wait state, and transfer state (figure 30).

The STS waiting state is the initialization state of the serial interface internal state. The serial interface

enters this state in one of two ways: either by changing the operation mode through a change in the data in

the port mode register, or by writing data into the serial mode register. In this state, the serial interface does

not operate even if the transmit clock is applied. If the STS instruction is executed then, the serial interface

shifts to the transmit clock wait state.

In the transmit clock wait state, the falling edge of the first transmit clock causes the serial interface to shift

to the transfer state, while the octal counter counts up and the serial data register shifts simultaneously. As

an exception, if the clock continuous output mode is selected, the serial interface stays in transmit clock

wait state while the transmit clock outputs continuously. The octal counter becomes 000 again after 8

external transmit clocks or by the execution of the STS instruction, the serial interface then returns to the

transmit clock wait state, and the serial interrupt request flag is set simultaneously. In the transfer state the

octal counter becomes 000 after 8 internal transmit clocks, the serial interface then enters the STS

instruction waiting state, and the serial interrupt request flag is set simultaneously.

When the internal transmit clock is selected, the transmit clock output is triggered by the execution of the

STS instruction, and stops after 8 clocks.

Program the SMR again to initialize the internal state of the serial interface when the PMRA is

programmed in the transfer state or in the transmit clock wait state. Then the serial interface goes into the

STS waiting state.

HD404816FS Datasheet(PDF) 59 Page - Renesas Technology Corp