E202075_HD404889 Datasheet, PDF (116/202 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip LCD Circuit

HD404889/HD404899/HD404878/HD404868 Series
Serial interface operating states:
The serial interface has the operating states shown in figure 63 in external clock mode and internal clock
mode.
STS instruction wait state
Serial clock wait state
Transfer state
Clock continuous output state (internal clock mode only)
• STS instruction wait state
Upon MCU reset ((00) and (10) in figure 63), the serial interface enters the STS instruction wait state.
In the STS instruction wait state, the internal state of the serial interface is initialized. Even if the serial
clock is input at this time, the serial interface will not operate. When the STS instruction is executed
((01), (11)), the serial interface enters the serial clock wait state.
• Serial clock wait state
The serial clock wait state is the interval from STS instruction execution until the first serial clock
falling edge. When the serial clock is input in the serial clock wait state ((02), (12)), the octal counter
begins counting, the contents of the serial data register (SRL) begin shifting, and the serial interface
enters the transfer state. However, if clock continuous output mode is selected in internal clock mode,
the serial interface enters the clock continuous output state ((17)) instead of the transfer state.
If a write to serial mode register 1 (SMR1) is performed in the serial clock wait state, the serial interface
enters the STS instruction wait state ((04), (14)).
• Transfer state
The transfer state is the interval from the first serial clock falling edge until the eighth serial clock rising
edge. In the transfer state, if an STS instruction is executed or if eight serial clocks have been input, the
octal counter is cleared to 000, and the serial interface makes a state transition. If an STS instruction is
executed ((05), (15)), the serial interface enters the serial clock wait state. After eight serial clocks have
been input, the serial interface enters the serial clock wait state ((03)) when in external clock mode, and
enters the STS instruction wait state ((13)) when in internal clock mode.
In internal clock mode, the serial clock stops after output of eight clocks.
If a write to serial mode register 1 (SMR1) is performed in the transfer state ((06), (16)), the serial
interface is initialized and enters the STS instruction wait state.
When the serial interface switches from the transfer state to another state, the octal counter is reset to
000 and the serial interrupt request flag (IFS) is set.
• Clock continuous output state (internal clock mode only)
In the clock continuous output state, no receive or transmit operation is performed, and the serial clock
is only output from the SCK pin. It is therefore effective in internal clock mode.
If the serial clock is input ((17)) when bit 3 (PMR33) of port mode register 3 (PMR3) is cleared to 0 and
the serial interface is in the serial clock wait state, a transition is made to the clock continuous output
state.
If a write to serial mode register 1 (SMR1) is performed in the clock continuous output state ((18)), the
serial interface enters the STS instruction wait state.
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