HD404356 Datasheet, PDF (62/100 Pages) Hitachi Semiconductor – 4-bit HMCS400-Series microcomputer

HD404358 Series
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.
The output level of the SO pin is invalid until the first data is output after MCU reset, or until the output
level control in idle states is performed.
Transfer Control: The serial interface is activated by the STS instruction. The octal counter is reset to 000
by this instruction, and it increments at the rising edge of the transmit clock. When the eighth transmit
clock signal is input or when serial transmission/receive is discontinued, the octal counter is reset to 000,
the serial interrupt request flag (IFS: $003, bit 2) is set, and the transfer stops.
When the prescaler output is selected as the transmit clock, the transmit clock frequency is selected as 4t_cyc
to 8192t_cyc by setting bits 0 to 2 (SMR0– SMR2) of serial mode register (SMR: $005) and bit 0 (PMRC0)
of port mode register C (PMRC: $025) as listed in table 28.
Table 28 Serial Transmit Clock (Prescaler Output)
PMRC
Bit 0
0
SMR
Bit 2
0
1
1
0
1
Bit 1
0
1
0
0
1
0
Bit 0
0
1
0
1
0
1
0
1
0
1
0
1
Prescaler Division Ratio
÷ 2048
÷ 512
÷ 128
÷ 32
÷8
÷2
÷ 4096
÷ 1024
÷ 256
÷ 64
÷ 16
÷4
Transmit Clock Frequency
4096t_cyc
1024t_cyc
256t_cyc
64t_cyc
16t_cyc
4t _cyc
8192t_cyc
2048t_cyc
512t_cyc
128t_cyc
32t_cyc
8t _cyc
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