NEC switch - Manual (Page 158)

CHAPTER 9 SERIAL INTERFACE 10
User’s Manual U12978EJ3V0UD
158
Table 9-2. Operating Mode Settings of Serial Interface 10
(1) Operation stop mode
CSIM10 PM22 P22 PM21 P21 PM20 P20 Start Shift P22/SI10 P21/SO10 P20/SCK10
CSIE10 DIR10 CSCK10 Bit Clock Pin Function Pin Function Pin Function
0 Ч Ч Ч Note 1 × Note 1 × Note 1 × Note 1 × Note 1 × Note 1 — — P22 P21 P20
Other than above Setting prohibited
(2) 3-wired serial I/O mode
CSIM10 PM22 P22 PM21 P21 PM20 P20 Start Shift P22/SI10 P21/SO10 P20/SCK10
CSIE10 DIR10 CSCK10 Bit Clock Pin Function Pin Function Pin Function
1 0 0 1 Note 2 × Note 2 0 1 1 × MSB External
clock
SI10 Note 2 SO10
(CMOS output)
SCK10 input
1 0 1 Internal
clock
SCK10 output
1 1 0 1 × LSB External
clock
SCK10 input
1 0 1 Internal
clock
SCK10 output
Other than above Setting prohibited
Notes 1. Can be used as port function.
2. If used only for transmission, can be used as P22 (CMOS input/output).
Remark ×: don’t care