MPC555
/
MPC556
SYSTEM CONFIGURATION AND PROTECTION
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
6-34
6.13.4.8 Periodic Interrupt Status and Control Register (PISCR)
The PISCR contains the interrupt request level and the interrupt status bit. It also con-
tains the controls for the 16 bits to be loaded into a modulus counter. This register can
be read or written at any time.
6.13.4.9 Periodic Interrupt Timer Count Register (PITC)
The PITC register contains the 16 bits to be loaded in a modulus counter. This register
is readable and writable at any time.
PISCR
— Periodic Interrupt Status and Control Register
0x2F C240
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSB
15
PIRQ
PS
RESERVED
PIE
PITF
PTE
HARD RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Table 6-18 PISCR Bit Descriptions
Bit(s)
Name
Description
0:7
PIRQ
Periodic interrupt request. These bits determine the interrupt priority level of the PIT. Refer to
for interrupt level encodings.
8
PS
Periodic interrupt status. This bit is set if the PIT issues an interrupt. The PIT issues an interrupt
after the modulus counter counts to zero. PS can be negated by writing a one to it. A write of zero
has no affect.
9:12
—
Reserved
13
PIE
Periodic interrupt enable. If this bit is set, the time base generates an interrupt when the PS bit
is set.
14
PITF
PIT freeze. If this bit is set, the PIT stops while FREEZE is asserted.
15
PTE
Periodic timer enable
0 = PIT stops counting and maintains current value
1 = PIT continues to decrement
PITC
— Periodic Interrupt Timer Count
0x2F C244
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
PITC
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
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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