HD404818 Datasheet, PDF (59/100 Pages) Hitachi Semiconductor – 16-digit LCD driver

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
register.
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
1
1
1
1
PMRA1
0
0
1
1
PMRA0
0
1
0
1
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.
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