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CHAPTER 4 RESET AND "EIT" PROCESSING
■ Saved Registers
Except in the case of reset processing, the values of the "PS" and "PC" are saved to the stack as designated
by the "SSP", regardless of the value of the "S" flag in the "CCR". No save operation is used in reset
processing.
Figure 4.2-3 illustrates the saving of the values of the "PC" and "PS" in "EIT" processing.
Figure 4.2-3 Saving "PC" and "PS" Values in "EIT" Processing
■ Recovery from EIT handler
RETI instruction is used for recovery from the EIT handler.
To insure the program execution results after recovery, it is required that all the contents of the CPU
register are saved.
Ensure that the PC and PS values in the stack are not overwritten unless necessary because those values,
saved in the stack at the occurrence of EIT, are recovered from the stack during the recovery sequence
using the RETI instruction. Be sure to set the "S" flag to "0" when the RETI instruction is executed.
Memory space
Immediately before interrupt
80000000
H
000FFC00H
SSP
TBR
12345678
H
000C0010H
PC
PS
FFFFFFFF
H
00000000H
7FFFFFF8H
7FFFFFFCH
offset: 000003B8H
Interrupt
IL=9
56781234
H
Memory space
Immediately after interrupt
000FFC00
H
SSP
TBR
56781234
H
00090010H
PC
PS
FFFFFFFF
H
00000000H
80000000H
7FFFFFFCH
7FFFFFF8H
offset: 000003B8H
56781234H
12345678H
000C0010H