User’s Manual U18172EJ2V0UD
308
APPENDIX D LIST OF CAUTIONS
This appendix lists cautions described in this document.
“Classification (hard/soft)” in table is as follows.
Hard: Cautions for microcontroller internal/external hardware
Soft: Cautions for software such as register settings or programs
(1/15)
Chapter
Cl
assi
fi
cati
on
Function Details
of
Function
Cautions Page
pp. 20,
Chapter 2
Hard
Pin
functions
P22/X2/ANI2,
P23/X1/ANI3
The P22/X2/ANI2, P23/X1/ANI3 pins are pulled down during reset.
21, 22, 23
Since reset signal generation makes the SP contents undefined, be sure to
initialize the SP before using the stack memory.
p. 35
Chapter 3
Soft
Memory
space
SP: stack
pointer
Stack pointers can be set only to the high-speed RAM area, and only the lower
10 bits can be actually set.
0FF00H is in the SFR area, not the high-speed RAM area, so it was converted
to 0FB00H that is in the high-speed RAM area. When the value is actually
pushed onto the stack, 1 is subtracted from 0FB00H to become 0FAFFH, but
that value is not in the high-speed RAM area, so it is converted to 0FEFFH,
which is the same value as when 0FF00H is set to the stack pointer.
p. 35
P22/X2/ANI2,
P23/X1/ANI3
The P22/X2/ANI2, P23/X1/ANI3 pins are pulled down during reset.
p. 51
P34
Because the P34 pin functions alternately as the RESET pin, if it is used as an
input port pin, the function to input an external reset signal to the RESET pin
cannot be used. The function of the port is selected by the option byte. For
details, refer to CHAPTER 15 OPTION BYTE.
Also, since the option byte is referenced after the reset release, if low level is
input to the RESET pin before the referencing, then the reset state is not
released. When it is used as an input port pin, connect the pull-up resistor.
p. 57
P21, P32
Because P21 and P32 are also used as external interrupt pins, the
corresponding interrupt request flag is set if each of these pins is set to the
output mode and its output level is changed. To use the port pin in the output
mode, therefore, set the corresponding interrupt mask flag to 1 in advance.
p. 59
PMC2: Port
mode control
register 2
When PMC20 to PMC23 are set to 1, the port function on the P20/ANI0 to
P23/ANI3 pins cannot be used. Moreover, be sure to set the pull-up resistor
option registers (PU20 to PU23) to 0 for the pins set to A/D converter mode.
p. 61
Chapter 4
Hard
Port
functions
−
Although a 1-bit memory manipulation instruction manipulates 1 bit, it accesses
a port in 8-bit units. Therefore, the contents of the output latch of a pin in the
input mode, even if it is not subject to manipulation by the instruction, are
undefined in a port with a mixture of inputs and outputs.
p. 63