Serial Interface Channel 1 Operations; Operation Stop Mode - NEC 78014Y Series User Manual

17.4 Serial Interface Channel 1 Operations

The following three operating modes are available to the serial interface channel 1.

• Operation stop mode

• 3-wire serial I/O mode
• 3-wire serial I/O mode with automatic transmit/receive function
17.4.1 Operation stop mode
Serial transfer is not carried out in the operation stop mode. Thus, power consumption can be reduced. The serial
I/O shift register 1 (SIO1) does not carry out shift operation either, and thus it can be used as a normal 8-bit register.
In the operation stop mode, the P20/SI1, P21/SO1, P22/SCK1, P23/STB and P24/BUSY pins can be used as
normal input/output ports.
(1) Register setting
The operation stop mode is set with the serial operating mode register 1 (CSIM1).
CSIM1 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets CSIM1 to 00H.
Symbol <7>
CSIM1 CSIE1
CSIE CSIM PM20 P20 PM21 P21 PM22 P22
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1 11
×
0
1 0
1
Notes 1. Can be used freely as port function.
2. Can be used as P20 (CMOS input/output) when only transmitter is used. (Set bit 7 (RE) of the automatic
data transmit/receive control register (ADTC) to 0.)
Remark ×
PMxx : Port mode register
Pxx
418
CHAPTER 17 SERIAL INTERFACE CHANNEL 1
6 <5> 4 3
DIR ATE 0 0
Shift Register
1 Operation
Operation stop
Note 1 Note 1 Note 1 Note 1 Note 1 Note 1
× × × × × ×
×
1 Operation
Note 2 Note 2
×
1 0 0 enable
0 1
: don't care
: Output latch of port
2 1 0 Address
0 CSIM11 CSIM12 FF68H
SI1/P20
Serial Clock Counter
Operation Pin Function
Control
Clear P20
(CMOS
input/output)
Count SI1
operation (Input)
When Reset R/W
00H R/W
SO1/P21 SCK1/P22
Pin Function Pin Function
P21 P22
(CMOS (CMOS
input/output) input/output)
Note 2 SO1 SCK1
(CMOS output) (Input)
SCK1
(CMOS output)