H8S2245 datasheet(459/818 Pages) RENESAS

459 / 818 page

Section 12 Serial Communication Interface (SCI)

Rev.3.00 Mar. 26, 2007 Page 417 of 772

REJ09B0355-0300

12.2.7

Serial Status Register (SSR)

TDRE

R/(W)*

RDRF

R/(W)*

ORER

R/(W)*

FER

R/(W)*

PER

R/(W)*

MPBT

R/W

TEND

MPB

Bit

Initial value

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

[Clearing conditions]

• When 0 is written to TDRE after reading TDRE = 1

• When the DTC* is activated by a TXI interrupt and write data to TDR

[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:

DTC can clear this bit only when DISEL is 0 with the transfer counter not being 0.

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