UPD78323LP datasheet(44/86 Pages) NEC

44 / 86 page

µPD78323, 78324

4.3

CONTEXT SWITCHING FUNCTION

This is the function to first select the specified register bank in hardware terms by generating an interrupt request or

executing BRKCS instruction, to branch the selected register bank to the vector address prestored in the register bank, and

also to stack the current PC and PSW contents into the register bank.

4.3.1

Context Switching Function at Interrupt Request

The context switching function start is enabled by setting the

× ×CSE bit preset at each interrupt request to 1.

If an unmasked interrupt request for which the context switching function has been enabled is generated in the EI state,

the register bank which is specified by the lower 3 bits of the lower address (even address) of the corresponding interrupt

vector table address is selected. The vector address prestored in the selected register bank is transferred to the PC, the

PC and PSW contents are saved into the register bank, and the operation is branched to the interrupt processing routine.

Return is by means of executing the RETCS instruction.

Figure 4-3. Context Switching at Interrupt Request

Banks

(0 to 7)

RBANK n

PSW

Exchange

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UPD78323LP Datasheet(PDF) 44 Page - NEC