r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 926

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 15 Serial Communication Interface (SCI, IrDA)
When turning on the power or switching between Smart Card interface mode and software
standby mode, the following procedures should be followed in order to maintain the clock duty
cycle.
Powering On: To secure the clock duty cycle from power-on, the following switching procedure
should be followed.
1. The initial state is port input and high impedance. Use a pull-up resistor or pull-down resistor
2. Fix the SCK pin to the specified output level with the CKE1 bit in SCR.
3. Set SMR and SCMR, and switch to Smart Card mode operation.
4. Set the CKE0 bit in SCR to 1 to start clock output.
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
2. Write 0 to the TE bit and RE bit in the serial control register (SCR) to halt transmit/receive
3. Write 0 to the CKE0 bit in SCR to halt the clock.
4. Wait for one serial clock cycle.
5. Make the transition to the software standby state.
When Returning to Smart Card Interface Mode from Software Standby Mode:
6. Exit the software standby state.
7. Write 1 to the CKE0 bit in SCR and output the clock. Signal generation is started with the
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REJ09B0467-0100
to fix the potential.
the value for the fixed output state in software standby mode.
operation. At the same time, set the CKE1 bit to the value for the fixed output state in software
standby mode.
During this interval, clock output is fixed at the specified level, with the duty cycle preserved.
normal duty cycle.