AN2109 Freescale Semiconductor / Motorola, AN2109 Datasheet - Page 13

• Manufacturer Part Number: AN2109
• Description: MPC555 Interrupts
• Manufacturer: Freescale Semiconductor / Motorola

3.3 Interrupt Sources: External IRQ Pins
As shown in the interrupt code table previously, the eight interrupt pins have unique interrupt codes. The
system designer must ensure the application’s higher priority external interrupts have lower number in-
terrupts. Each external interrupt pin has a mask bit in the SIMASK register to enable it. IRQ[0:7] have
six priorities and interrupt code. The hardware design must connect higher priority interrup signals to
the lower number of interrupt pins, such as IRQ[1] or IRQ[2].
IRQ[0]
vector offset, but does not cause an actual reset. Hence the exception vector will be 0x100 instead
of 0x500. If the RESET exception routine needs to determine the cause of the reset, then the reset sta-
tus register (RSR) and SIPEND[IRQ0] bit are examined.
is a special case. This is non-maskable and causes a NMI exception. It uses the reset exception
NOTES:
Other lower priority or masked interrupt requests can be examined at any time by
reading the SIPEND register. If no unmasked interrupt request is pending, the In-
terrupt Code has a default value of 0x3C.
Because IRQ[0] can cause a nonmaskable exception, it can cause an irrecover-
able condition. Therefore, it should not be used for a normal application input.
0 (highest)
1. IRQ[0] Input Pin is a special case. See
Priority
16-31
10
11
12
13
14
15
1
2
3
4
5
6
7
8
9
Freescale Semiconductor, Inc.
For More Information On This Product,
Interrupt Source
Table 8 Interrupt Priority and Codes
IRQ[0] Input Pin
IRQ[1] Input Pin
IRQ[2] Input Pin
IRQ[3] Input Pin
IRQ[4] Input Pin
IRQ[5] Input Pin
IRQ[6] Input Pin
IRQ[7] Input Pin
Rev. 0, 26 July 2001
MPC555 Interrupts
Reserved
Level 0
Level 1
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
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CAUTION
1
NOTE
3.3 Interrupt Sources: External IRQ
Interrupt Code
00000000
00000100
00001000
00001100
00010000
00010100
00011000
00011100
00100000
00100100
00101000
00101100
00110000
00110100
00111000
00111100
(Binary)
—
Interrupt Code
(Default value)
(Hex)
0x1C
0x2C
0x3C
0x10
0x14
0x18
0x20
0x24
0x28
0x30
0x34
0x38
0xC
0x0
0x4
0x8
—
Pins.
MOTOROLA
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