PSoC1 CY8C29466-24PVXI operates at supply voltage 3.0V to 3.6V or 4.75V to 5.25V.
On the other hand, looking at DC Programming Specifications in the data sheet,
Vddp: VDD for programming and erase requires min 4.5V / max 5.5V.
Customers use PSoC at Vdd=3.3V. Even in this case, is 5V different from Vdd=3.3V needed for on-board programming?
Programming/erasing under 4.5V for PSoC1 may lead to PSoC1 unstable Flash data.
Yes. Even though customers use this device at Vdd=3.3V, 5V programming/erasing is required to guarantee the life cycle of Flash data.