
254
CHAPTER 16 INTERRUPT FUNCTION
User
’
s Manual U15017EJ2V0UD
Figure 16-9. Return from BRKCS Instruction Software Interrupt (RETCSB Instruction Operation)
16.5 Operand Error Interrupt Acknowledgment Operation
An operand error interrupt is generated when the data obtained by inverting all the bits of the 3rd byte of the operand
of an MOV STBC, #byte instruction or LOCATION instruction or an MOV WDM, #byte instruction does not match the
4th byte of the operand. Operand error interrupts cannot be disabled.
When an operand error interrupt is generated, the program status word (PSW) and the start address of the
instruction that caused the error are saved to the stack, the IE flag is cleared to 0, the vector table value is loaded
into the program counter (PC), and a branch is performed (within the base area only).
As the address saved to the stack is the start address of the instruction in which the error occurred, simply writing
an RETB instruction at the end of the operand error interrupt service program will result in generation of another
operand error interrupt. You should therefore either process the address in the stack or initialize the program by
referring to
16.12 Restoring Interrupt Function to Initial State
.
16.6 Non-Maskable Interrupt Acknowledgment Operation
Non-maskable interrupts are acknowledged even in the interrupt disabled state.
Except in the cases described in
16.9 When Interrupt Requests and Macro Service Are Temporarily Held
Pending
, a non-maskable interrupt request is acknowledged immediately. When a non-maskable interrupt request
is acknowledged, the program status word (PSW) and program counter (PC) are saved in that order to the stack,
the IE flag of the PSW is cleared to 0, the in-service priority register (ISPR) bit corresponding to the acknowledged
non-maskable interrupt is set to 1, the vector table contents are loaded into the PC, and a branch is performed. The
ISPR bit that is set to 1 is the WDTS bit.
Even if the same non-maskable interrupt request is generated more than once during execution of the non-
maskable interrupt service program, only one non-maskable interrupt is acknowledged after completion of the non-
maskable interrupt service program.
PC
19-16
PC
15-0
<1> Restoration
<3> Transfer
<4> Restoration
(To original
register bank)
<2> Restoration
PSW
V
VP
U
UP
T
E
W
L
RETCSB instruction operand
Register Bank n (n = 0 to 7)
A
R5
R7
D
H
B
X
R4
R6
C