UPD784044 Datasheet, PDF (43/90 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLER

µPD784044(A), 784046(A)
8.3 Context Switching
A specific register bank is selected by hardware when an interrupt request is generated or when the BRKCS
instruction is executed.
Execution branches to the vector address stored in advance to the selected register bank, and the current
contents of the program counter (PC) and program status word (PSW) are stacked to the register bank.
The branch destination address must be in a range of 0 to FFFFH.
Figure 8-1. Context Switching Operation When Interrupt Request Is Generated
0000B
< 7 > Transfer
PC19-16
PC15_0
< 6 > Exchange
< 2 > Save
(bits 8 through
11 of temporary
register)
< 5 > Save
Temporary register
< 1 > Save
PSW
Register bank
Register bank n (n = 0 to 7)
(0 to 7)
A
X
B
C
R5
R4
R7
R6
V
VP
U
UP
< 3 > Select register bank (RBS0 to RBS2←n)
T
D
E
W
H
L
< 4 > RSS←0
IE ←0
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