HD404369 Datasheet, PDF (76/117 Pages) Hitachi Semiconductor – 4-bit HMCS400-Series microcomputer

HD404369 Series
SO
SCK
SI
Idle
controller
I/O
controller
Octal
counter (OC)
Clock
1/2
1/2
Serial interrupt
request flag
(IFS)
Serial data
register (SR)
Transfer
control
signal
System
clock
ø_PER
Selector
3
Serial mode
register
(SMR)
Prescaler S (PSS)
Port mode
register C
(PMRC)
Figure 58 Serial Interface Block Diagram
Serial Interface Operation
Selecting and Changing the Operating Mode: Table 27 lists the serial interface’s operating modes. To
select an operating mode, use one of these combinations of port mode register A (PMRA: $004) and the
serial mode register (SMR: $005) settings; to change the operating mode, always initialize the serial
interface internally by writing data to the serial mode register. Note that the serial interface is initialized by
writing data to the serial mode register. Refer to the following Serial Mode Register section for details.
Pin Setting: The R0₀/SCK pin is controlled by writing data to the serial mode register (SMR: $005). The
R0₁/SI and R0₂/SO pins are controlled by writing data to port mode register A (PMRA: $004). Refer to the
following Registers for Serial Interface section for details.
Transmit Clock Source Setting: The transmit clock source is set by writing data to the serial mode
register (SMR: $005) and port mode register C (PMRC: $025). Refer to the following Registers for Serial
Interface section for details.
Data Setting: Transmit data is set by writing data to the serial data register (SRL: $006, SRU, $007).
Receive data is obtained by reading the contents of the serial data register. The serial data is shifted by the
transmit clock and is input from or output to an external system.
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