HD404459 Datasheet, PDF (84/122 Pages) Renesas Technology Corp – 4-bit HMCS400-series microcomputers

HD404459 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
φ_PER
Selector
3
Serial mode
register A
(SMRA)
Prescaler S (PSS)
Serial mode
register B
(SMRB)
Figure 67 Serial Interface Block Diagram
Serial Interface Operation
Selecting and Changing the Operating Mode: To select an operating mode, use one of these
combinations of port mode register A (PMRA: $004) and serial mode register A (SMRA: $005) settings
(table 28); to change the operating mode of the serial interface, always initialize the serial interface
internally by writing data to serial mode register A. Note that the serial interface is initialized by writing
data to serial mode register A. Refer to the following section, Registers for Serial Interface, for details.
Pin Setting: The R4₁/SCK pin is controlled by writing data to serial mode register A (SMRA: $005). Pins
R4₂/SI and R4₃/SO are controlled by writing data to port mode register A (PMRA: $004). Refer to the
following section, Registers for Serial Interface, for details.
Transmit Clock Source Setting: The transmit clock source of the serial interface is set by writing data to
serial mode register A (SMRA: $005) and serial mode register B (SMRB: $028). Refer to the following
section, Registers for Serial Interface, for details.
Data Setting: Transmit data of the serial interface is set by writing data to the serial data register (SRL:
$006, SRU: $007). Receive data of the serial interface is obtained by reading the contents of the serial data
register. The serial data is shifted by each serial interface transmit clock and is input from or output to an
external system.
82