I'm using the Renesas Synergy starter kit SK-S7G2. I noticed the CPU is connected to an IRQ signal. Does anyone know what this IRQ is used for, e.g. sleep wake-up, ethernet PHY, LAN, or is it even needed?
The SK-S7G2 provides access to many IRQ pins of the MCU. These IRQ inputs are available in each of the application headers in the kit. IRQ is basically an external interrupt pin that is used for measuring external signal charactristics such as frequency, counts, pulse width, etc. It can also be clubbed with various other interfaces such as I2C (For LCD touchscreen function in this case), Ethernet, Button Input, etc.
Depending upon the trigger mode selected in configuration(rising edge, falling edge, level) the external interrupt could divert the mcu to a specific interrupt vector address. Physically a call instruction to your interrupt call back function resides at this address.
Once you figure out how to use the interrupts, it is very easy to design an efficient multi-tasking system.
There are multiple external IRQ signals that can be used to signal the CPU that an external event has occurred. Examples are IRQ's for Touch, Ethernet, LCD, etc. Whether you use them or not will depend on your application.
The trend in modern microcontrollers is to have lots of interrupts. The S7G2 datasheet that I looked at lists 16 separate IRQ inputs that you can program. What's the thing connected to on the schematic? If it's just going to an external header, then it's there for you to do whatever you want with it.
Thank you all for your information! It is helpful.