m3819 Renesas Electronics Corporation., m3819 Datasheet - Page 186

• Manufacturer Part Number: m3819
• Description: Mitsubishi 8-bit Single-chip Microcomputer 740 Family / 38000 Series
• Manufacturer: Renesas Electronics Corporation.

3. APPENDIX
172
3.1.6 Notes on clock synchronous serial I/O
<Note 2>
When the data register (port latch) of an I/O port is modified with the bit managing instruction*, the value of the
unspecified bit may be changed.
Reason
The bit managing instructions are read-modify-write form instructions for reading and writing data by a byte unit.
Accordingly, when these instructions are executed on a bit of the data register of an I/O port, the following is executed
to all bits of the data register.
Note the following :
*
<Note 3>
When not using the A-D converter, connect the A-D converter power source AV
Reason
If the AV
<Note>
When an external clock is used as the synchronous clock for data transmission, set the transmit enable bit to “1” at
“H” of the S
bit managing instructions : SEB and CLB instruction
As for a bit which is set to an input port : The pin state is read in the CPU, and is written to this bit after bit managing.
As for a bit which is set to an output port : The bit value is read in the CPU, and is written to this bit after bit managing.
Even when a port which is set as an output port is changed for an input port, its data register holds the output data.
As for a bit of which is set to an input port , its value may be changed even when not specified with a bit managing
AV
instruction in case where the pin state differs from its data register contents
SS
: Connect to the V
SS
CLK
pin is opened, the microcomputer may have a failure because of noise or others.
input level. Also, write data to the transmit buffer register at “H” of the S
SS
pin
3819 Group USER’S MANUAL
SS
3.1 Notes on use
MITSUBISHI MICROCOMPUTER
pin as follows :
CLK
3819 Group
input level.