242
CHAPTER 14 SERIAL INTERFACE (SIO3)
Preliminary User’s Manual U16035EJ1V0UM
14.4 Operations of Serial Interface
This section explains the two modes of the serial interface (SIO3n).
14.4.1 Operation stop mode
Because the serial transfer is not performed during this mode, the power consumption can be reduced.
In addition, pins can be used as normal I/O ports.
(1) Register settings
Operation stop mode is set by the serial operation mode register 3n (CSIM3n).
CSIM3n is set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets CSIM3n to 00H.
Address: FFB0H (SIO30), FFB8H (SIO31) After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
CSIM3n
CSIE3n
0
0
0
0
MODEn
SCL3n1
SCL3n0
CSIE3n
Enable/disable specification for SIO3n
Shift register operation
Serial counter
Port
0
Operation disabled
Clear
Port function
Note 1
1
Operation enabled
Count operation enabled
Serial fu port function
Note 2
Notes 1.
When CSIE3n = 0 (SIO3n operation stop status), the pins SI3n, SO3n, and SCK3n can be used for
port functions.
2.
When CSIE3n = 1 (SIO3n operation enabled status), the SI3n pin can be used as a port pin if only
the transmit function is used, and the SO3n pin can be used as a port pin if only the receive-only mode
is used.
Remark
n = 0, 1