UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 483

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

In the 3-wire serial I/O mode, the SO0 pin functions as a CMOS push-pull output.
Remark If the PD784026 is connected to a 2-wire serial I/O device, a buffer should be connected to the SO0 pin as
(b) LSB-first
SO0 (Output)
shown in Figure 17-7. In the example shown in Figure 17-7, the output level is inverted by the buffer, and
therefore the inverse of the data to be output should be written to SIO.
Also, non-connection of an internal pull-up resistor should be specified for the P33/SO0 pin.
SI0 (Input)
INTCSI
SCK0*
Figure 17-7 Example of Connection to 2-Wire Serial I/O Device
PD784026
Figure 17-6 3-Wire Serial I/O Mode Timing (2/2)
CHAPTER 17 CLOCKED SERIAL INTERFACE
1
DO0 DO1 DO2 DO3 DO4 DO5 DO6 DO7
SCK0
DI0
SO0
SI0
2
Start of transfer synchronized with fall of SCK0
Execution of instruction that writes to SIO, etc.
DI1
3
DI2
4
DI3
5
DI4
6
DI5
7
DI6
8
SCK
SIO
2-Wire Serial I/O
Device
DI7
Transfer End
Interrupt Generation
* Master CPU: Output
Slave CPU : Input
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