Timing In Three-Wire Serial I/O Mode; Sample Connection With A Device Having Two-Wire Serial I/O - NEC PD78212 User Manual

µ PD78214 Sub-Series
Note
SCK
SI (input)
SO (output)
INTCSI
In three-wire serial I/O mode, the SO pin sends a CMOS push-pull output.
Remark When connecting the device to a device having two-wire serial I/O, connect a buffer to the SO pin as shown in Fig. 10-6. In the example
shown in Fig. 10-6, the buffer inverts the output level. Invert the data to be output and write the inverted data into the SIO. Do not
connect the built-in pull-up resistor to pin P33/SO.
Fig. 10-6 Sample Connection with a Device Having Two-Wire Serial I/O
If transmission and reception are time-shared, and if the µ PD78214 can control the output level of the SIO pin of
a device containing two-wire serial I/O, the SI pin and SO pin can be connected directly. To do this, disable
transmission by other devices while the µ PD78214 is transmitting data.
266
Fig. 10-5 Timing in Three-Wire Serial I/O Mode
1 2 3 4
DI7 DI6 DI5 DI4
DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0
Transfer starts in synchronization with SCK falling edge
Executing instruction to write data to SIO
Notes Master CPU : Output
Slave CPU : Input
µ
PD78214
SCK
SI
SO
5 6 7 8
DI3 DI2 DI1 DI0
Transfer end interrupt occurs
2-wire serial
I/O device
SCK
SIO