H83814 Datasheet, PDF (230/456 Pages) Renesas Technology Corp – single-chip microcomputers

When an external clock is used, data is transmitted in synchronization with the serial clock input
at pin SCK₁. After data transmission is complete, an overrun occurs if the serial clock continues
to be input; no data is transmitted and the SCSR1 overrun error flag (bit ORER) is set to 1.
While transmission is stopped, the output value of pin SO₁ can be changed by rewriting bit SOL
in SCSR1.
• Receiving
A receive operation is carried out as follows.
— Set bit SI1 in port mode register 3 (PMR3) to 1, making pin P3₁/SI₁ the SI₁ input pin. Also
set bit SCK1 in PMR3 to 1, making pin P3₀/SCK₁ the SCK₁ I/O pin.
— Clear bit SNC1 in SCR1 to 0, and set bit SNC0 to 1 or 0, designating 8- or 16-bit
synchronous transfer mode. Select the serial clock in bits CKS3 to CKS0. Writing data to
SCR1 initializes the internal state of SCI1.
— Set the SCSR1 start flag (STF) to 1. SCI1 starts operating and receives data at pin SI₁.
— After data reception is complete, bit IRRS1 in interrupt request register 1 (IRR1) is set to 1.
— Read the received data from SDRL and SDRU, as follows.
8-bit transfer mode: SDRL
16-bit transfer mode: Upper byte in SDRU, lower byte in SDRL
— After data reception is complete, an overrun occurs if the serial clock continues to be input;
no data is received and the SCSR1 overrun error flag (bit ORER) is set to 1.
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