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When switching from transmit mode to receive mode, first confirm that the transmit operation has
been completed, then start from initialization, clearing TE to 0 and setting RE to 1. The TEND
flag can be used to check that the transmit operation has been completed.
Fixing Clock Output: When the GM bit is set to 1 in SMR, clock output can be fixed by means
of the CKE1 and CKE0 bits in SCR. The minimum clock pulse width can be set to the specified
width in this case.
Figure 13.9 shows the timing for fixing clock output. In this example, GM = 1, CKE1 = 0, and the
CKE0 bit is controlled.
SCK
Interrupt Operations: The smart card interface has three interrupt sources: transmit-data-empty
(TXI), transmit/receive-error (ERI), and receive-data-full (RXI). The transmit-end interrupt
request (TEI) is not available in smart card mode.
A TXI interrupt is requested when the TEND flag is set to 1 in SSR. An RXI interrupt is requested
when the RDRF flag is set to 1 in SSR. An ERI interrupt is requested when the ORER, PER, or
ERS flag is set to 1 in SSR. These relationships are shown in table 13.8.
Table 13.8 Smart Card Interface Mode Operating States and Interrupt Sources
Operating State
Transmit Mode
Normal operation
Error
Receive Mode
Normal operation
Error
Specified pulse
width
CKE1 value
SCR write
(CKE0 = 0)
Figure 13.9 Timing for Fixing Cock Output
Flag
TEND
ERS
RDRF
PER, ORER
Specified pulse
width
SCR write
(CKE0 = 1)
Enable Bit
TIE
RIE
RIE
RIE
Interrupt Source
TXI
ERI
RXI
ERI
391
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