There is a note in the Pins-component datasheet telling
If the Pin Interrupt is used to wake the part up from sleep or hibernate low-power mode, the Interrupt component connected to the Pins irq terminal may not have InterruptType set to "RISING_EDGE."
This will probably explain why the interrupt is behaving as you told.
For stop mode -
http://www.cypress.com/?rID=38267 AN54460 - PSoC® 3, PSoC 4, and PSoC 5LP Interrupts
http://www.cypress.com/?rID=95069 AN90799 - PSoC® 4 Interrupts
http://www.cypress.com/?rID=93401 AN86439 - PSoC® 4 - Using GPIO Pins
http://www.cypress.com/?rID=78797 AN86233 - PSoC® 4 Low-Power Modes and Power Reduction Techniques
http://www.cypress.com/?rID=96072 AN90114 - PSoC® 4000 Family Low-Power System Design Techniques
Thanks for trying to help, but evidently there's a misunderstanding. Please read my post again:
Deep Sleep != Stop
IRQ on FALLING edge
The same method is working on the CY8CKIT-042, but not the target with the same PSoC and I am totally baffled
The datasheet does not talk about the irq, it talkes about the isr that is attached to the irq-signal. The isr must be configured as falling edge.
It is and has been configured for falling edge. Please pardon my preference for hardware-oriented terminology. The edge is determined by hardware confguration. ISR refers to software.
So it's working now: The solution was to NOT disable the ILO on the target board. This same code was working on CY8CKIT-042, but why? I wonder if the bootoader code on that board locks a WDT so that the ILO cannot be disabled.
Does anyone know?