HD64F3644PV Datasheet, PDF (347/551 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 10 Serial Communication Interface
When clock output mode is selected, SCI3 outputs 8 serial clock pulses. When an external clock is
selected, data is output in synchronization with the input clock.
Serial data is transmitted from the TXD pin in order from the LSB (bit 0) to the MSB (bit 7).
When the MSB (bit 7) is sent, checks bit TDRE. If bit TDRE is cleared to 0, SCI3 transfers data
from TDR to TSR, and starts transmission of the next frame. If bit TDRE is set to 1, SCI3 sets bit
TEND to 1 in SSR, and after sending the MSB (bit 7), retains the MSB state. If bit TEIE in SCR3
is set to 1 at this time, a TEI request is made.
After transmission ends, the SCK₃ pin is fixed at the high level.
Note: Transmission is not possible if an error flag (OER, FER, or PER) that indicates the data
reception status is set to 1. Check that these error flags (OER, FER, and PER) are all
cleared to 0 before a transmit operation.
Figure 10.17 shows an example of the operation when transmitting in synchronous mode.
Serial
clock
Serial
data
Bit 0 Bit 1
Bit 7
Bit 0
Bit 1
Bit 6
Bit 7
TDRE
TEND
1 frame
1 frame
LSI
TXI request
operation
TDRE cleared TXI request
to 0
TEI request
User
processing
Data written
to TDR
Figure 10.17 Example of Operation when Transmitting in Synchronous Mode
Rev. 6.00 Sep 12, 2006 page 325 of 526
REJ09B0326-0600