Datasheet

Section 14 Serial Communication Interface (SCI)
Rev.6.00 Sep. 27, 2007 Page 611 of 1268
REJ09B0220-0600
14.2.7 Serial Status Register (SSR)
Bit : 7 6 5 4 3 2 1 0
TDRE RDRF ORER FER PER TEND MPB MPBT
Initial value : 1 0 0 0 0 1 0 0
R/W : R/(W)
*
R/(W)
*
R/(W)
*
R/(W)
*
R/(W)
*
R R R/W
Note: * Only 0 can be written, to clear the flag.
SSR is an 8-bit register containing status flags that indicate the operating status of the SCI, and
multiprocessor bits.
SSR can be read or written to by the CPU at all times. However, 1 cannot be written to flags
TDRE, RDRF, ORER, PER, and FER. Also note that in order to clear these flags they must be
read as 1 beforehand. The TEND flag and MPB flag are read-only flags and cannot be modified.
SSR is initialized to H'84 by a reset, and in standby mode or module stop mode.
Bit 7—Transmit Data Register Empty (TDRE): Indicates that data has been transferred from
TDR to TSR and the next serial data can be written to TDR.
Bit 7
TDRE Description
0 [Clearing conditions]
• When 0 is written to TDRE after reading TDRE = 1
• When the DMAC
*
or DTC is activated by a TXI interrupt and writes data to TDR
1 [Setting conditions] (Initial value)
• When the TE bit in SCR is 0
• When data is transferred from TDR to TSR and data can be written to TDR
Note: * The DMAC is not supported in the H8S/2321.