Notes On Switching From Sck Pins To Port Pins - Renesas H8S/2100 Series Hardware Manual

Section 15 Serial Communication Interface (SCI)
15.9.7

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 15.40.
SCK/Port
Data
TE
C/A
CKE1
CKE0
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/A = 1, CKE1 = 0, CKE0 = 0, and TE = 1.
1. End serial data transmission
2. TE bit = 0
3. CKE1 bit = 1
4. C/A bit = 0 (switch to port output)
5. CKE1 bit = 0
SCK/Port
Data
TE
C/A
CKE1
CKE0
Figure 15.38 Prevention of Low Pulse Output at Switching from SCK Pins to Port Pins
Rev. 1.00 Apr. 28, 2008 Page 466 of 994
REJ09B0452-0100
1. Transmission end
Bit 6 Bit 7
2. TE = 0
Figure 15.37 Switching from SCK Pins to Port Pins
1. Transmission end
Bit 6 Bit 7
2. TE = 0
Low pulse of half a cycle
4. Low pulse output
3. C/A = 0
4. C/A = 0
3. CKE1 = 1
High output
5. CKE1 = 0