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7.1.1.7
Software Interrupts
Software interrupts can be initiated by the INT instruction. Any of the 256 possible interrupts
can be initiated by the INT instruction. INT 21h causes an interrupt to the vector located at
00084h in the interrupt vector table. INT FFh causes an interrupt to the vector located at
003FCh in the interrupt vector table. Software interrupts are not maskable and are not
affected by the setting of the IF flag.
7.1.1.8
Software Exceptions
A software exception interrupt occurs when an instruction causes an interrupt due to some
condition in the processor. Interrupt types 00h, 01h, 03h, 04h, 05h, 06h, and 07h are
software exception interrupts. Software exceptions are not maskable and are not affected
by the setting of the IF flag.
Table 7-1
Am186EM and Am188EM Microcontroller Interrupt Types
Interrupt Name
Divide Error Exception
Trace Interrupt
Non-Maskable Interrupt (NMI)
Breakpoint Interrupt
INTO Detected Overflow Exception
Array Bounds Exception
Unused Opcode Exception
ESC Opcode Exception
Timer 0 Interrupt
Timer 1 Interrupt
Timer 2 Interrupt
Reserved for AMD Use
DMA 0 Interrupt
DMA 1 Interrupt
INT0 Interrupt
INT1 Interrupt
INT2 Interrupt
INT3 Interrupt
INT4 Interrupt
Watchdog Timer Interrupt
Asynchronous Serial Port Interrupt
Reserved for AMD Use
Notes:
1. Interrupts generated as a result of an instruction execution.
2. Trace is performed in the same manner as 80C186 and 80C188.
3. An ESC opcode causes a trap. This is part of the 80C186 and 80C188 co-processor interface, which is not
supported on the Am186EM.
4. All three timers constitute one source of request to the interrupt controller. As such, they share the same priority
level with respect to other interrupt sources. However, the timers have a defined priority order among themselves
(2A>2B>2C).
5. The interrupt types of these sources are programmable in slave mode.
6. Not available in slave mode.
Interrupt
Vector Table
Type
Address
00h
00h
01h
04h
02h
08h
03h
0Ch
04h
10h
05h
14h
06h
18h
07h
1Ch
08h
20h
12h
48h
13h
4Ch
09h
0Ah
28h
0Bh
2Ch
0Ch
30h
0Dh
34h
0Eh
38h
0Fh
3Ch
10h
40h
11h
44h
14h
50h
15h–1Fh
Interrupt Control Unit
EOI
Overall
Related
Type
Priority
Instructions
N/A
1
DIV, IDIV
N/A
1A
N/A
1B
N/A
1
N/A
1
N/A
1
BOUND
N/A
1
Undefined
Opcodes
N/A
1
ESC Opcodes
08
2A
08
2B
08
2C
0A
3
0B
4
0C
5
0D
6
0E
7
0F
8
10
9
11
9
14
9
Notes
1
All
2
INT 3
1
INTO
1
1
1
1, 3
4, 5
4, 5
4, 5
5
5
6
6
6
7-3
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