HD404328 Datasheet, PDF (55/96 Pages) Hitachi Semiconductor – 4 BIT SINGLE CHIP MICROCOMPUTER

HD404328 Series
Transmit clock
Serial output
data
1
2
3
4
5
6
7
8
LSB
MSB
Serial input data
latch timing
Figure 31 Timing of Serial Interface Output
Selecting and Changing Operating Mode: Table 28 lists the serial interface’s operating modes. To
select an operating mode, use one of these combinations of PMR and SMR settings; to change the
operating mode, always initialize the serial interface internally by writing data to the SMR.
Table 28 Serial Interface Operating Modes
SMR
Bit 3
1
PMRA
Bit 1
0
1
Bit 0
0
1
0
1
Operating Mode
Continuous clock output mode
Transmit mode
Receive mode
Transmit/receive mode
Serial Interface Operation: Three operating modes are provided for the serial interface; transitions
between them are shown in figure 32.
In STS wait state, the serial interface is initialized and the transmit clock is ignored. If the STS instruction
is then executed, the serial interface enters transmit clock wait state.
In transmit clock wait state, input of the transmit clock increments the octal clock, shifts the serial clock
register, and activates serial transmission. However, note that if clock output mode is selected, the transmit
clock is continuously output but data is not transmitted.
During transfer state, 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.
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.
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