MOTOROLA
Chapter 11. System Interface Unit
11-31
Part III. Configuration
Figure 11-28. Periodic Interrupt Timer Block Diagram
The time-out period is calculated as follows:
Solving this equation using a 32.768-KHz external clock gives:
This gives a range from 122
m
s (PITC = 0x0000) to 8 seconds (PITC = 0xFFFF).
11.11.1 Periodic Interrupt Status and Control Register (PISCR)
The read/write periodic interrupt status and control register (PISCR) contains the interrupt
request level and status bits. It also controls the 16 bits to be loaded in a modulus counter.
Note that PISCR is a keyed register. It must be unlocked in PISCRK before it can be
written.
Bit
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Field
PIRQ
PS
Ñ
PIE
PITF PTE
Reset
0000_0000_0000_0000
R/W
R/W
Addr
(IMMR & 0xFFFF0000) + 0x240
Figure 11-29. Periodic Interrupt Status and Control Register (PISCR)
Clock
Disable
PIT
Interrupt
PITRTCLK
Clock
16-Bit
Modulus Counter
PTE
PITC
PS
PIE
FRZ
PIT
period
PITC
1
+
F
pitrtclk
-------------------------
PITC
1
+
ExternalClock
1
o
or
o
128
------------------------------------------
è
ø
æ
ö
4
¸
------------------------------------------------------------
=
=
PITperiod
PITC
1
+
8192
-------------------------
=
Содержание MPC860 PowerQUICC
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