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In a receive operation, an RXI interrupt request is generated when the RDRF flag in SSR is set to
1. If the RXI request is designated beforehand as a DMAC or DTC activation source, the DMAC
or DTC will be activated by the RXI request, and transfer of the receive data will be carried out.
The RDRF flag is cleared to 0 automatically when data transfer is performed by the DMAC or
DTC. If an error occurs, an error flag is set but the RDRF flag is not. Consequently, the DMAC or
DTC is not activated, but instead, an ERI interrupt request is sent to the CPU. Therefore, the error
flag should be cleared.
Note: For details of operation in block transfer mode, see section 11.4, SCI Interrupts.
12.3.7
Operation in GSM Mode
Switching the Mode: When switching between smart card interface mode and software standby
mode, the following switching procedure should be followed in order to maintain the clock duty.
• When changing from smart card interface mode to software standby mode
[1] Set the data register (DR) and data direction register (DDR) corresponding to the SCK pin to
the value for the fixed output state in software standby mode.
[2] Write 0 to the TE bit and RE bit in the serial control register (SCR) to halt the transmit/receive
operation. At the same time, set the CKE1 bit to the value for the fixed output state in software
standby mode.
[3] Write 0 to the CKE0 bit in SCR to halt the clock.
[4] Wait for one serial clock period.
During this interval, clock output is fixed at the specified level, with the duty preserved.
[5] Write H'00 to SMR and SCMR.
[6] Make the transition to the software standby state.
• When returning to smart card interface mode from software standby mode
[7] Exit the software standby state.
[8] Set the CKE1 bit in SCR to the value for the fixed output state (current SCK pin state) when
software standby mode is initiated.
[9] Set smart card interface mode and output the clock. Signal generation is started with the
normal duty.
477
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