HD6433044 Datasheet, PDF (528/867 Pages) Hitachi Semiconductor – Hitachi Single-Chip Microcomputer

2. Write 0 to 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 to 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 to 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
mode
Normal operation
(1)(2)(3)
(4) (5)(6)
(1) (2)(3)
Figure 14.9 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 in SCR to 1 to start clock output.
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