Usage Notes; Module Stop Mode Setting; Break Detection And Processing; Mark State And Break Detection - Hitachi H8S/2628 Hardware Manual

14.9

Usage Notes

14.9.1

Module Stop Mode Setting

SCI operation can be disabled or enabled using the module stop control register. The initial setting
is for SCI operation to be halted. Register access is enabled by clearing module stop mode. For
details, refer to section 21, Power-Down Modes.
14.9.2

Break Detection and Processing

When framing error detection is performed, a break can be detected by reading the RxD pin value
directly. In a break, the input from the RxD pin becomes all 0s, setting the FER flag, and possibly
the PER flag. Note that as the SCI continues the receive operation after receiving a break, even if
the FER flag is cleared to 0, it will be set to 1 again.
14.9.3

Mark State and Break Detection

When TE is 0, the TxD pin is used as an I/O port whose direction (input or output) and level are
determined by DR and DDR. This can be used to set the TxD pin to mark state (high level) or send
a break during serial data transmission. To maintain the communication line at mark state until TE
is set to 1, set both DDR and DR to 1. As TE is cleared to 0 at this point, the TxD pin becomes an
I/O port, and 1 is output from the TxD pin. To send a break during serial transmission, first set
DDR to 1 and DR to 0, and then clear TE to 0. When TE is cleared to 0, the transmitter is
initialized regardless of the current transmission state, the TxD pin becomes an I/O port, and 0 is
output from the TxD pin.
14.9.4

Receive Error Flags and Transmit Operations (Clocked Synchronous Mode Only)

Transmission cannot be started when a receive error flag (ORER, PER, or FER) is set to 1, even if
the TDRE flag is cleared to 0. Be sure to clear the receive error flags to 0 before starting
transmission. Note also that receive error flags cannot be cleared to 0 even if the RE bit is cleared
to 0.
Rev. 1.0, 09/02, page 353 of 568