APPENDIX D MEASURES AGAINST NOISE
S1C17651 TECHNICAL MANUAL
Seiko Epson Corporation
AP-D-1
Appendix D Measures Against Noise
To improve noise immunity, take measures against noise as follows:
Noise Measures for VDD and VSS Power Supply Pins
The IC will malfunction at the instant when noise falling below the rated voltage is input. Take measures on the
circuit board, including close patterns for circuit board power supply circuits, noise-filtering decoupling capaci-
tors, and surge/noise prevention components on the power supply line.
For the recommended patterns on the circuit board, see “Mounting Precautions” in Appendix.
Noise Measures for #RESET Pin
The pull-up resistor for the #RESET pin included in this product has a relatively high impedance of 100 k
W to
500 k
W and is not noise-resistant. Extraneous noise may pull the #RESET pin down to a low level and this will
cause the IC to reset. Therefore, the circuit board must be designed properly taking noise measures into consid-
eration.
For the recommended patterns on the circuit board, see “Mounting Precautions” in Appendix.
Noise Measures for Oscillator Pins
The oscillator input pins must pass a signal of small amplitude, so they are hypersensitive to noise. Therefore,
the circuit board must be designed properly taking noise measures into consideration.
For the recommended patterns on the circuit board, see “Mounting Precautions” in Appendix.
Noise Measures for Debug Pins
This product provides the input/output pins (DCLK, DST2, and DSIO) to connect ICDmini (S5U1C17001H)
for debugging. If noise is input to these pins, the S1C17 Core may enter debug mode. To prevent unexpected
transitions to debug mode caused by extraneous noise, switch the DCLK, DST2, and DSIO pins to general-
purpose I/O port pins within the initialization routine when the debug functions are not used.
For details of the pin functions and the function switch control, see the “I/O Ports (P)” chapter.
Note: Do not perform the function switching shown above when the application is under development,
as the debug functions must be used. The debugging cannot be performed after the pin function is
switched. The above processing must be added after the application development has completed
and debugging is no longer necessary.
The DSIO pin should be pulled up with a 10 k
W resistor when using the debug pin functions. The pull-up resis-
tor for the DSIO pin included in this product has a relatively high impedance of 100 k
W to 500 kW and is not
noise-resistant.
Noise Measures for Interrupt Input Pins
This product is able to generate a port input interrupt when the input signal changes. The interrupt is generated
when an input signal edge is detected, therefore, an interrupt may occur if the signal changes due to extraneous
noise.
To prevent occurrence of unexpected interrupts due to extraneous noise, enable the chattering filter circuit when
using the port input interrupt.
For details of the port input interrupt and chattering filter circuit, see the “I/O Ports (P)” chapter.