In the processing for unused pins described in the uPD70F3107A data sheet, P00..P07 are described as “Input: Connect to VSS”. Is it possible to pull the pins up to VDD when setting the input pins of the I/O ports (initial values)?
A1 Yes, it is OK to pull them up to VDD. In old devices, when pins were pulled up by resistors, the pin voltage would rise slowly at power-up and be detected as a low-to-high signal change, resulting in the occurrence of an interrupt. This processing was adopted to prevent this, and still remains in some devices. In this device, the NMI valid edge is not specified in the initial state and thus this problem does not occur.
Related Questions
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