Rev. 1.0, 09/02, page 344 of 568
14.7.5 Initialization
Before transmitting and receiving data, initialize the SCI as described below. Initialization is also
necessary when switching from transmit mode to receive mode, or vice versa.
1. Clear the TE and RE bits in SCR to 0.
2. Clear the error flags ERS, PER, and ORER in SSR to 0.
3. Set the GM, BLK, O/
E
, BCP0, BCP1, CKS0, CKS1 bits in SMR. Set the PE bit to 1.
4. Set the SMIF, SDIR, and SINV bits in SCMR.
When the SMIF bit is set to 1, the TxD and RxD pins are both switched from ports to SCI pins,
and are placed in the high-impedance state.
5. Set the value corresponding to the bit rate in BRR.
6. Set the CKE0 and CKE1 bits in SCR. Clear the TIE, RIE, TE, RE, MPIE, and TEIE bits to 0.
If the CKE0 bit is set to 1, the clock is output from the SCK pin.
7. Wait at least one bit interval, then set the TIE, RIE, TE, and RE bits in SCR. Do not set the TE
bit and RE bit at the same time, except for self-diagnosis.
To switch from receive mode to transmit mode, after checking that the SCI has finished reception,
initialize the SCI, and set RE to 0 and TE to 1. Whether SCI has finished reception or not can be
checked with the RDRF, PER, or ORER flags. To switch from transmit mode to receive mode,
after checking that the SCI has finished transmission, initialize the SCI, and set TE to 0 and RE to
1. Whether SCI has finished transmission or not can be checked with the TEND flag.
14.7.6
Data Transmission (Except for Block Transfer Mode)
As data transmission in Smart Card interface mode involves error signal sampling and
retransmission processing, the operations are different from those in normal serial communication
interface mode (except for block transfer mode). Figure 14.26 illustrates the retransfer operation
when the SCI is in transmit mode.
1. If an error signal is sent back from the receiving end after transmission of one frame is
complete, the ERS bit in SSR is set to 1. If the RIE bit in SCR is enabled at this time, an ERI
interrupt request is generated. The ERS bit in SSR should be kept cleared to 0 until the next
parity bit is sampled.
2. The TEND bit in SSR is not set for a frame in which an error signal indicating an abnormality
is received. Data is retransferred from TDR to TSR, and retransmitted automatically.
3. If an error signal is not sent back from the receiving end, the ERS bit in SSR is not set.
Transmission of one frame, including a retransfer, is judged to have been completed, and the
TEND bit in SSR is set to 1. If the TIE bit in SCR is enabled at this time, a TXI interrupt
request is generated. Writing transmit data to TDR transfers the next transmit data.
Summary of Contents for H8S/2627
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