VR4111..( uPD30111 ; planed to discontinue)

There are two locations to be set, the Cause register and the software interrupt register (SOFTINTREG) of the interrupt controller.

How can I set two sources for the cause register and 4 sources for SOFTINTREG?

Since the two types of software interrupts operate independently of each other, there are no settings for their interrelations, etc.
Each software interrupt is explained below.

• Software interrupt by CP0 Cause register (2 sources)
  This interrupt is generated by manipulating the IP(1:0) bit of the CP0 Cause register by software.
  The interrupt that is usually generated is an interrupt exception, and the exception source is specified by reading the IP(1:0) field of the Cause register.
  This software interrupt is not related to the ICU, and it cannot be masked by the ICU.
  
  
• Software interrupt by ICU SOFTINTREG register (4 sources)
  This interrupt is generated by manipulating the SOFTINTR(3:0) bit of the SOFTINTREG register by software.
  The interrupt that is usually generated is an interrupt exception, and is the INT0 interrupt (IP2).
  The occurrence of an interrupt can be ascertained using the SOFTINTR bit of SYSINT1REG of the ICU, and which of the 4 sources to use to generate the interrupt can be specified by SOFTINTR(3:0) of the SOFTINTREG register.
  Moreover, masking by the SOFTINTR bit of MSYSINT1REG is also possible.
  Since interrupts can be controlled by the ICU and exceptions other than those of the timer, etc., can be covered by INT0, it seems that this interrupt is more often used.