AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 115

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

7.3.13
Figure 7-16
Figure 7-17
exit:
End-of-Interrupt Register
(EOI, Offset 22h)
(Master Mode)
The End-of-Interrupt (EOI) register is a write-only register. The in-service flags in the In-
Service register (see Section 7.3.8 on page 7-22) are reset by writing to the EOI register.
Before executing the IRET instruction that ends an interrupt service routine (ISR), the ISR
should write to the EOI register to reset the IS bit for the interrupt.
The specific EOI reset is the most secure method to use for resetting IS bits. Figure 7-16
shows example code for a specific EOI reset. See Table 7-1 on page 7-4 for specific EOI
values.
Example EOI Assembly Code
End-of-Interrupt Register
Bit 15: Non-Specific EOI (NSPEC)—The NSPEC bit determines the type of EOI command.
When written as a 1, NSPEC indicates non-specific EOI. When written as a 0, NSPEC
indicates the specific EOI interrupt type is in S4–S0.
Bits 14–5: Reserved
Bits 4–0: Source Interrupt Type (S4–S0)—Specifies the EOI type of the interrupt that is
currently being processed. See Table 7-1 on page 7-4.
...
...
...
mov ax,int_type
mov dx, 0ff22h
out dx,ax
popa
iret
NSPEC
15
Interrupt Control Unit
Reserved
;ISR code
;load the interrupt type in ax
;write the interrupt type to EOI
;return from interrupt
7
S4–S0
0
7-27