NEC PD78214 - Manual (Page 295)

266
µ
PD78214 Sub-Series
Fig. 10-5 Timing in Three-Wire Serial I/O Mode
Notes Master CPU : Output
Slave CPU : Input
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
SCK
2-wire serial
I/O device
SI
SO
SCK
SIO
PD78214 µ
If transmission and reception are time-shared, and if the
µPD78214 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
µPD78214 is transmitting data.
1 2 3 4 5 6 7 8
DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0
SCK Note
SI (input)
DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0 SO (output)
INTCSI
Transfer end interrupt occurs
Transfer starts in synchronization with SCK falling edge
Executing instruction to write data to SIO