HD64F2145 datasheet(431/829 Pages) RENESAS

431 / 829 page

Rev. 2.0, 08/02, page 391 of 788

15.9.8

Notes on Switching from SCK Pins to Port Pins

When SCK pins are switched to port pins after transmission has completed, pins are enabled for

port output after outputting a low pulse of half a cycle as shown in figure 15.28.

SCK/Port

CKE0

CKE1

Data

1. Transmission end

2. TE = 0

3. C/

= 0

4. Low pulse output

Bit 6

Bit 7

Low pulse of half a cycle

Figure 15.28 Switching from SCK Pins to Port Pins

To prevent the low pulse output that is generated when switching the SCK pins to the port pins,

specify the SCK pins for input (pull up the SCK/port pins externally), and follow the procedure

below with DDR = 1, DR = 1, C/

$ = 1, CKE1 = 0, CKE1 = 0, and TE = 1.

1. End serial data transmission

2. TE bit = 0

3. CKE1 bit = 1

4. C/

$ bit = 0 (switch to port output)

5. CKE1 bit = 0

SCK/Port

CKE0

CKE1

Data

1. Transmission end

2. TE = 0

4. C/

= 0

3. CKE1 = 1

5. CKE1 = 0

Bit 6

Bit 7

High output

Figure 15.29 Prevention of Low Pulse Output at Switching from SCK Pins to Port Pins

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