H8SSLASH2225 datasheet(716/1071 Pages) RENESAS

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Section 15 Serial Communication Interface (SCI)

Rev. 5.00 Aug 08, 2006 page 630 of 982

REJ09B0054-0500

15.10.7 Switching from SCK Pin Function to Port Pin Function

• Problem in Operation

When switching the SCK pin function to the output port function (high-level output) by

making the following settings while DDR = 1, DR = 1, C/

A = 1, CKE1 = 0, CKE0 = 0, and TE

= 1 (synchronous mode), low-level output occurs for one half-cycle.

1. End of serial data transmission

2. TE bit = 0

3. C/

A bit = 0… Switchover to port output

4. Occurrence of low-level output

SCK/port

Data

CKE1

CKE0

Bit 7

Bit 6

1. End of transmission

4. Low-level output

3. C/

A = 0

2. TE = 0

Half-cycle low-level output

Figure 15.43 Operation when Switching from SCK Pin Function to Port Pin Function

• Sample Procedure for Avoiding Low-Level Output

As this sample procedure temporarily places the SCK pin in the input state, the SCK/port pin

should be pulled up beforehand with an external circuit.

With DDR = 1, DR = 1, C/

A = 1, CKE1 = 0, CKE0 = 0, and TE = 1, make the following

settings in the order shown.

1. End of serial data transmission

2. TE bit = 0

3. CKE1 bit = 1

4. C/

A bit = 0… Switchover to port output

5. CKE1 bit = 0

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