Interrupts
Am186™CC/CH/CU Microcontrollers User’s Manual
7-9
■
Software Interrupt: An interrupt initiated by the INT or INTO software instruction, or by
a software exception. A software interrupt does not affect the IF flag.
■
Software Exception: A software interrupt that occurs when an instruction causes a
particular condition in the processor. A software exception does not affect the IF flag.
■
Trace Interrupt: The trace interrupt is the highest priority interrupt. It is a software
interrupt in that it is initiated by software, but unlike other software interrupts, it does
clears the IF flag.
■
Hardware Interrupt: Any one of the maskable interrupts, the NMI, and the watchdog
timer interrupt. When a hardware interrupt is generated, the IF flag is cleared unless in
polled mode.
7.5.3
Interrupt Sequence
The following sections describe how the microcontroller services interrupts.
7.5.3.1
Requesting the Interrupt
When an interrupt is requested, the internal interrupt controller verifies that the interrupt is
enabled and that there are no higher priority interrupt requests being serviced or pending.
If the interrupt request is granted, the interrupt controller uses the interrupt type to access
a vector from the interrupt vector table.
Each interrupt source has a corresponding interrupt type. Each interrupt type has a four-
byte vector available in the interrupt vector table. The interrupt vector table is located in the
1024 bytes from 00000h to 003FFh. Each four-byte vector consists of a 16-bit offset (IP)
value and a 16-bit segment (CS) value. The 8-bit interrupt type is shifted left two bit positions
(multiplied by four) to generate the index into the interrupt vector table, as shown in Figure
7-2.
Figure 7-2
Interrupt Vector Translation
When an interrupt is taken, the type is multiplied by four and the processor fetches the
pointer to the interrupt service routine from that interrupt vector address. Table 7-3 on
page 7-12 shows a list of the types assigned to each interrupt source, as well as the interrupt
vector address and the overall priority. The first entries in the table are the nonmaskable
and software interrupt sources. The overall priority numbers are used only to resolve two
interrupts that have identical programmable priority requests pending. In these cases, the
type with the lowest overall priority number gets the highest priority. For overall priority
numbers with letters, the lower letter is considered of higher priority (e.g., 2A is a higher
priority than 2B).
Interrupt Vector
Table Locations
EF
01
AB
CD
12
34
56
78
Interrupt Vector
for Type 1
Interrupt Vector
for Type 0
0008 (2 • 4)
0004 (1 • 4)
0000 (0 • 4)
Interrupt Vector Type 1 = EF01:ABCD
Interrupt Vector Type 0 = 1234:5678
Содержание Am186 CC
Страница 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Страница 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Страница 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Страница 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Страница 39: ...Architectural Overview Am186 CC CH CU Microcontrollers User s Manual 1 15 Figure 1 6 32 Channel Linecard CH CC...
Страница 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Страница 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Страница 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Страница 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Страница 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...