HD404612FS datasheet(56/91 Pages) RENESAS

56 / 91 page

HD404618 Series

During transmission, the input of eight clocks or the execution of the STS instruction sets the octal counter

to 000, and the serial interface enters transmit clock wait state. If the state changes from transmit to another

state, the serial interrupt request flag is set by the octal counter reaching 000.

octal counter = 000

transmit clock disabled

STS instruction wait state

Transmit clock

8 transmit clocks (external clock)

STS instruction

←

(IFS

(octal counter = 000)

≠

Transmit clock wait state

Transfer state

(octal counter

000)

Figure 33 Serial Interface Mode Transitions

In this state, if the internal clock has been selected, the transmit clock is output in answer to the execution

of the STS instruction, but serial transmission is inhibited after the eighth clock is output.

If port mode register A (PMRA) is written to in transmit clock wait state or during transmission, the serial

mode register (SMR) must be written to, to initialize the serial interface. The serial interface then enters

STS wait state.

If the serial interface shifts from transfer state to another state, the octal counter returns to 000, setting the

serial interrupt request flag.

Transmit Clock Error Detection: The serial interface will malfunction if a spurious pulse caused by

external noise conflicts with a normal transmit clock during transmission. A transmit clock error of this

type can be detected as shown in figure 34.

If more than eight transmit clocks are input in transmit clock wait state, the serial interface state changes to

transfer, transmit clock wait, then back to transfer.

If the serial interface is set to STS wait state by writing data to the SMR after the serial interrupt request

flag has been reset, the flag is set again.

HD404612FS датащи(PDF) 56 Page - Renesas Technology Corp