Renesas H8/3067 Series User Manual page 518

Section 13 Serial Communication Interface
The CPU can always read and write SSR, but cannot write 1 in the TDRE, RDRF, ORER, PER,
and FER flags. These flags can be cleared to 0 only if they have first been read while set to 1. The
TEND and MPB flags are read-only bits that cannot be written.
SSR is initialized to H'84 by a reset and in standby mode.
Bit 7—Transmit Data Register Empty (TDRE): Indicates that the SCI has loaded transmit data
from TDR into TSR and the next serial data can be written in TDR.
Bit 7
TDRE Description
0 TDR contains valid transmit data
Clearing conditions
Read TDRE when TDRE = 1, then write 0 in TDRE
The DMAC writes data in TDR
1 TDR does not contain valid transmit data
Setting conditions
The chip is reset or enters standby mode
The TE bit in SCR is cleared to 0
TDR contents are loaded into TSR, so new data can be written in TDR
Bit 6—Receive Data Register Full (RDRF): Indicates that RDR contains new receive data.
Bit 6
RDRF Description
0 RDR does not contain new receive data
Clearing conditions
The chip is reset or enters standby mode
Read RDRF when RDRF = 1, then write 0 in RDRF
The DMAC reads data from RDR
1 RDR contains new receive data
Setting condition
Serial data is received normally and transferred from RSR to RDR
Note: The RDR contents and the RDRF flag are not affected by detection of receive errors or by
clearing of the RE bit to 0 in SCR. They retain their previous values. If the RDRF flag is still
set to 1 when reception of the next data ends, an overrun error will occur and the receive
data will be lost.
Rev. 4.00 Jan 26, 2006 page 494 of 938
REJ09B0276-0400
(Initial value)
(Initial value)