HD64F3642AHV Datasheet, PDF (306/551 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 10 Serial Communication Interface
SDRL is an 8-bit read/write register. It is used as the data register in 8-bit transfer, and as the data
register for the lower 8 bits in 16-bit transfer (SDRU is used for the upper 8 bits).
In 8-bit transfer, data written to SDRL is output from pin SO₁ starting from the least significant bit
(LSB). This data is then replaced by LSB-first data input at pin SI₁, which is shifted in the
direction from the most significant bit (MSB) toward the LSB.
In 16-bit transfer, operation is the same as for 8-bit transfer, except that input data is fed in via
SDRU.
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 undefined.
10.2.3 Operation in Synchronous Mode
Data can be sent and received in an 8-bit or 16-bit format, with an internal or external clock
selected as the clock source. Overrun errors can be detected when an external clock is used.
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 SCK₁ becomes the clock output pin. When
continuous clock output mode is selected (SCR1 bits SNC1 and SNC0 are set to 10), the clock
signal (φ/1024 to φ/2) selected in bits CKS2 to CKS0 is output continuously from pin SCK₁. When
an external clock is used, pin SCK₁ is the clock input pin.
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 rising edge. Receive data is latched at the rising edge of the
serial clock.
SCK₁
SO₁ /SI₁
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
Figure 10.2 Transfer Format
Rev. 6.00 Sep 12, 2006 page 284 of 526
REJ09B0326-0600