
APPENDIX E SUMMARY OF PRECAUTIONS
AP-E-8
EPSON
S1C33E07 TECHNICAL MANUAL
General-Purpose I/O Ports (GPIO)
After an initial reset, the cause-of-interrupt flags become indeterminate. To prevent generation of an
unwanted interrupt or IDMA request, be sure to reset the flags in a program.
To prevent regeneration of interrupts due to the same cause of interrupt following the occurrence of an
interrupt, always be sure to reset the cause-of-interrupt flag before resetting the PSR or executing the reti
instruction.
When using an port input interrupt as the trigger to restart from the SLEEP mode, an interrupt will occur due
to the input signal level even if edge interrupt is specified as an interrupt condition. The signal level to restart
the CPU is as follows according to the signal edge selected:
If a rising-edge interrupt is set, the CPU restarts when the input signal goes to a high level.
If a falling-edge interrupt is set, the CPU restarts when the input signal goes to a low level.
When a falling edge interrupt is selected to restart after the slp instruction is executed, the operation is as
follows.
If the interrupt port is already at a low level when the slp instruction is executed, the CPU enters SLEEP
mode instantaneously and restarts immediately afterward.
If the interrupt port is at a high level when the slp instruction is executed, the SLEEP mode continues until
the port goes low.
Therefore, design the system assuming that the CPU can restart normally due to the signal level at the
interrupt port, not an edge interrupt, when restarting the CPU from SLEEP mode using a port input interrupt.
To use the P15–P17 and P34–P36 pins that are configured as the debug interface pins by default for general-
purpose inputs/outputs, clear TRCMUX (D0/0x300014) to 0.
TRCMUX: P15–17, P34–36 Debug Function Select Bit in the Debug Port MUX Register (D0/0x300014)
Note, however, that the PC trace function of the debugger cannot be used when TRCMUX (D0/0x300014) is
set to 0.
Even if the port input interrupt condition is set to falling edge, the input pulse width must be longer than 1
cycle of the port operating clock (= MCLK) to be certain an interrupt will be generated.
A/D Converter (ADC)
Before setting the conversion mode, start/end channels, etc. for the A/D converter, be sure to disable ADE
(D2/0x300544). A change in settings while the A/D converter is enabled could cause it to operate erratically.
ADE: A/D Enable Bit in the A/D Control/Status Register (D2/0x300544)
In consideration of the conversion accuracy, we recommend that the A/D conversion clock be min. 16 kHz to
max. 2 MHz.
Do not start an A/D conversion when the clock supplied from the prescaler to the A/D converter is turned off,
and do not turn off the prescaler's clock output when an A/D conversion is underway, as doing so could cause
the A/D converter to operate erratically.
After an initial reset, FADE (D1/0x300287) and FADC (D0/0x300287) become indeterminate. To prevent
generation of an unwanted interrupt or IDMA request, be sure to reset these flags in a program.
FADE: A/D Conversion Completion Interrupt Cause Flag in the Port Input 4–7, RTC, A/D Interrupt Cause
Flag Register (D1/0x300287)
FADC: A/D Out-of-Range Interrupt Cause Flag in the Port Input 4–7, RTC, A/D Interrupt Cause Flag
Register (D0/0x300287)
To prevent the regeneration of interrupts due to the same cause of interrupt following the occurrence an
interrupt, always be sure to reset the cause-of-interrupt flag before setting the PSR again or executing the reti
instruction.
When the A/D converter is set to enabled state, a current flows between AVDD and VSS, and power is
consumed, even when A/D operations are not performed. Therefore, when the A/D converter is not used, it
must be set to the disabled state (default 0 setting of ADE (D2/0x300544)).