r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 944

• Manufacturer Part Number: r4f2426
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 15 Serial Communication Interface (SCI, IrDA)
15.10.5 Relation between Writes to TDR and the TDRE Flag
The TDRE flag in SSR is a status flag that indicates that transmit data has been transferred from
TDR to TSR. When the SCI transfers data from TDR to TSR, the TDRE flag is set to 1.
Data can be written to TDR regardless of the state of the TDRE flag. However, if new data is
written to TDR when the TDRE flag is cleared to 0, the data stored in TDR will be lost since it has
not yet been transferred to TSR. It is therefore essential to check that the TDRE flag is set to 1
before writing transmit data to TDR.
15.10.6 Restrictions on Use of DMAC or DTC
• When an external clock source is used as the serial clock, the transmit clock should not be
• When RDR is read by the DMAC or DTC, be sure to set the activation source to the relevant
Rev. 1.00 Sep. 19, 2008 Page 916 of 1270
REJ09B0466-0100
input until at least 5 φ clock cycles after TDR is updated by the DMAC or DTC. Incorrect
operation may occur if the transmit clock is input within 4 φ clocks after TDR is updated.
(Figure 15.35)
SCI receive-data-full interrupt (RXI).
SCK
TDRE
Serial data
Note: When operating on an external clock, set t > 4 clocks.
Figure 15.35 Example of Synchronous Transmission Using DTC
t
LSB
D0
D1
D2
D3
D4
D5
D6
D7