MPC555
/
MPC556
SYSTEM CONFIGURATION AND PROTECTION
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
6-26
*IRQ0 of the SIPEND register is not affected by the setting or clearing of the IRM0 bit of the SIMASK register. IRQ0 is
a non-maskable interrupt.
6.13.2.3 SIU Interrupt Edge Level Register (SIEL)
The SIEL is a 32-bit read/write register. Each pair of bits corresponds to an external
interrupt request. The EDx bit, if set, specifies that a falling edge in the corresponding
IRQ line will be detected as an interrupt request. When the EDx bit is 0, a low logical
level in the IRQ line will be detected as an interrupt request. The WMx (wake-up mask)
bit, if set, indicates that an interrupt request detection in the corresponding line causes
the MPC555 / MPC556 to exit low-power mode.
6.13.2.4 SIU Interrupt Vector Register
The SIVEC is a 32-bit read-only register that contains an 8-bit code representing the
unmasked interrupt source of the highest priority level. The SIVEC can be read as ei-
ther a byte, half word, or word. When read as a byte, a branch table can be used in
which each entry contains one instruction (branch). When read as a half-word, each
entry can contain a full routine of up to 256 instructions. The interrupt code is defined
such that its two least significant bits are 0, thus allowing indexing into the table.
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
LSB
31
RESERVED
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
SIEL
— SIU Interrupt Edge Level Register
0x2F C018
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ED0
WM0
ED1
WM1
ED2
WM2
ED3
WM3
ED4
WM4
ED5
WM5
ED6
WM6
ED7
WM7
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
LSB
31
RESERVED
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
SIVEC
— SIU Interrupt Vector
0x2F C01C
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
INTERRUPT CODE
RESERVED
RESET:
0
0
1
1
1
1
0
0
0
0
0
0
0
0
0
0
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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