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Rev. 5.00, 09/03, page 440 of 760
14.2.7 Serial Status Register (SCSSR)
The serial status register (SCSSR) is an 8-bit register containing multiprocessor bit values, and
status flags that indicate the SCI operating state.
The CPU can always read and write to SCSSR, but cannot write 1 to the status flags (TDRE,
RDRF, ORER, PER, and FER). These flags can be cleared to 0 only if they have first been read
(after being set to 1). Bits 2 (TEND) and 1 (MPB) are read-only bits that cannot be written.
SCSSR is initialized to H'84 by a reset and in standby or module standby mode.
Bit:76543210
TDRE RDRF ORER FER PER TEND MPB MPBT
Initial value:10000100
R/W: R/(W)
*
R/(W)
*
R/(W)
*
R/(W)
*
R/(W)
*
RRR/W
Note: * The only value that can be written is 0 to clear the flag.
Bit 7—Transmit Data Register Empty (TDRE): Indicates that the SCI has loaded transmit data
from SCTDR into SCTSR and new serial transmit data can be written in SCTDR.
Bit 7: TDRE Description
0 SCTDR contains valid transmit data
[Clearing condition]
TDRE is cleared to 0 when software reads TDRE after it has been set to 1.
1 SCTDR does not contain valid transmit data (Initial value)
[Setting conditions]
(1) TDRE is set to 1 when the chip is reset or enters standby mode.
(2) The TE bit in the serial control register (SCSCR) is cleared to 0.
(3) SCTDR contents are loaded into SCTSR, so new data can be written in
SCTDR.