HD6433636SW datasheet(233/418 Pages) RENESAS

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SDRL must be written or read only after data transmission or reception is complete. If this register

is read or written while a data transfer is in progress, the data contents are not guaranteed.

The SDRL value upon reset is not fixed.

10.2.3

Operation

Data can be sent and received in an 8-bit or 16-bit format, synchronized to an internal or external

clock. Overrun errors can be detected when an external clock is used.

(1) Clock

The serial clock can be selected from a choice of eight internal clocks and an external clock. When

an internal clock source is selected, pin SCK

1 becomes the clock output pin. When continuous

clock output mode is selected (SCR1 bits SNC1 and SNC0 are set to 10), the clock signal (ø/1024

to ø/2) selected in bits CKS2 to CKS0 is output continuously from pin SCK

1. When an external

clock is used, pin SCK

1 is the clock input pin.

(2) Data transfer format

Figure 10.2 shows the data transfer format. Data is sent and received starting from the least

significant bit, in LSB-first format. Transmit data is output from one falling edge of the serial

clock until the next falling edge. Receive data is latched at the rising edge of the serial clock.

SCK

SO /SI

Bit 0

Bit 1

Bit 2

Bit 3

Bit 4

Bit 5

Bit 6

Bit 7

Figure 10.2 Transfer Format

(3) Data transfer Operations

Transmitting: A transmit operation is carried out as follows.

1. Set bits SO1 and SCK1 in PMR2 to 1, selecting the SO

1 and SCK1 pin functions. If necessary,

set bit POF1 in PMR2 for NMOS open drain output at pin SO

2. 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.

3. Write transmit data in SDRL and SDRU, as follows.

8-bit transfer mode:

SDRL

16-bit transfer mode: Upper byte in SDRU, lower byte in SDRL

4. Set the SCSR1 start flag (STF) to 1. SCI1 starts operating and outputs transmit data at pin SO

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