Clock Output Control - Renesas H8S/2100 Series Hardware Manual

6-bit single-chip microcomputer

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Section 14 Serial Communication Interface (SCI)

Clock Output Control

Clock output can be fixed using the CKE1 and CKE0 bits in SCR when the GM bit in SMR is set

to 1. Specifically, the minimum width of a clock pulse can be specified.

Figure 14.31 shows an example of clock output fixing timing when the CKE0 bit is controlled

with GM = 1 and CKE1 = 0.

Specified pulse width

Figure 14.31 Clock Output Fixing Timing

At power-on and transitions to/from software standby mode, use the following procedure to secure

the appropriate clock duty ratio.

To secure the appropriate clock duty ratio simultaneously with power-on, use the following

1. Initially, port input is enabled in the high-impedance state. To fix the potential level, use a

pull-up or pull-down resistor.

2. Fix the SCK pin to the specified output using the CKE1 bit in SCR.

3. Set SMR and SCMR to enable smart card interface mode.

4. Set the CKE0 bit in SCR to 1 to start clock output.

Rev. 1.00 May 09, 2008 Page 418 of 954

REJ09B0462-0100