3069RF-ZTAT Datasheet, PDF (558/1003 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER

Examples of Operation in GSM Mode: When switching between smart card interface mode and
software standby mode, use the following procedures to maintain the clock duty cycle.
• Switching from smart card interface mode to software standby mode
1. Set the P9₄ data register (DR) and data direction register (DDR) to the values for the fixed
output state in software standby mode.
2. Write 0 in the TE and RE bits in the serial control register (SCR) to stop transmit/receive
operations. At the same time, set the CKE1 bit to the value for the fixed output state in
software standby mode.
3. Write 0 in the CKE0 bit in SCR to stop the clock.
4. Wait for one serial clock cycle. During this period, the duty cycle is preserved and clock
output is fixed at the specified level.
5. Write H'00 in the serial mode register (SMR) and smart card mode register (SCMR).
6. Make the transition to the software standby state.
• Returning from software standby mode to smart card interface mode
1. Clear the software standby state.
2. Set the CKE1 bit in SCR to the value for the fixed output state at the start of software standby
(the current P94 pin state).
3. Set smart card interface mode and output the clock. Clock signal generation is started with the
normal duty cycle.
Normal operation
Software
standby
Normal operation
(1) (2) (3)
(4) (5) (6) (1) (2) (3)
Figure 14.10 Procedure for Stopping and Restarting the Clock
Use the following procedure to secure the clock duty cycle after powering on.
1. The initial state is port input and high impedance. Use pull-up or pull-down resistors to fix the
potential.
2. Fix at the output specified by the CKE1 bit in SCR.
3. Set SMR and SCMR, and switch to smart card interface mode operation.
4. Set the CKE0 bit to 1 in SCR to start clock output.
Rev. 5.0, 09/04, page 536 of 978