Section 16 Serial Communication Interface (SCI, IrDA, and CRC)
Rev. 3.00 Jan 25, 2006 page 462 of 872
REJ09B0286-0300
16.10.3 Mark State and Break Detection
When the TE bit in SCR 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 of the port. 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. Since the TE bit 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 the TE bit to 0. When the
TE bit 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.
16.10.4 Receive Error Flags and Transmit Operations (Clocked Synchronous Mode Only)
Transmission cannot be started when a receive error flag (ORER, FER, or RER) in SSR is set to 1,
even if the TDRE flag in SSR is cleared to 0. Be sure to clear the receive error flags to 0 before
starting transmission. Note also that the receive error flags cannot be cleared to 0 even if the RE
bit in SCR is cleared to 0.
16.10.5 Relation between Writing to TDR and TDRE Flag
Data can be written to TDR irrespective of the TDRE flag status in SSR. However, if the new data
is written to TDR when the TDRE flag is 0, that is, when the previous data has not been
transferred to TSR yet, the previous data in TDR is lost. Be sure to write transmit data to TDR
after verifying that the TDRE flag is set to 1.
16.10.6 Restrictions on Using DTC or RFU
When the external clock source is used as a synchronization clock, update TDR by the DTC or
RFU and wait for at least five
φ
clock cycles before allowing the transmit clock to be input. If the
transmit clock is input within four clock cycles after TDR modification, the SCI may malfunction
(figure 16.38).
When using the DTC or RFU to read RDR, be sure to set the receive end interrupt source (RXI) as
a DTC or RFU activation source.
Содержание H8S/2158
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Страница 126: ...Section 4 Exception Handling Rev 3 00 Jan 25 2006 page 72 of 872 REJ09B0286 0300...
Страница 198: ...Section 6 Bus Controller Rev 3 00 Jan 25 2006 page 144 of 872 REJ09B0286 0300...
Страница 326: ...Section 10 8 Bit PWM Timer PWM Rev 3 00 Jan 25 2006 page 272 of 872 REJ09B0286 0300...
Страница 440: ...Section 15 Watchdog Timer WDT Rev 3 00 Jan 25 2006 page 386 of 872 REJ09B0286 0300...
Страница 606: ...Section 17 I 2 C Bus Interface IIC Rev 3 00 Jan 25 2006 page 552 of 872 REJ09B0286 0300...
Страница 742: ...Section 19 Multimedia Card Interface MCIF Rev 3 00 Jan 25 2006 page 688 of 872 REJ09B0286 0300...
Страница 744: ...Section 20 Encryption Operation Circuit DES and GF Rev 3 00 Jan 25 2006 page 690 of 872 REJ09B0286 0300...
Страница 750: ...Section 21 D A Converter Rev 3 00 Jan 25 2006 page 696 of 872 REJ09B0286 0300...
Страница 768: ...Section 22 A D Converter Rev 3 00 Jan 25 2006 page 714 of 872 REJ09B0286 0300...
Страница 770: ...Section 23 RAM Rev 3 00 Jan 25 2006 page 716 of 872 REJ09B0286 0300...
Страница 824: ...Section 26 Clock Pulse Generator Rev 3 00 Jan 25 2006 page 770 of 872 REJ09B0286 0300...
Страница 844: ...Section 27 Power Down Modes Rev 3 00 Jan 25 2006 page 790 of 872 REJ09B0286 0300...
Страница 878: ...Section 28 List of Registers Rev 3 00 Jan 25 2006 page 824 of 872 REJ09B0286 0300...
Страница 926: ...Index Rev 3 00 Jan 25 2006 page 872 of 872 REJ09B0286 0300...