Programmable Interrupt Timers (PIT0–PIT3)
Freescale Semiconductor
29-5
29.2.2
PIT Modulus Register (PMR
n
)
The 16-bit read/write PMR
n
contains the timer modulus value loaded into the PIT counter when the count
reaches 0x0000 and the PCSR
n
[RLD] bit is set.
When the PCSR
n
[OVW] bit is set, PMR
n
is transparent, and the value written to PMR
n
is immediately
loaded into the PIT counter. The prescaler counter is reset (0xFFFF) anytime a new value is loaded into
the PIT counter and also during reset. Reading the PMR
n
returns the value written in the modulus latch.
Reset initializes PMR
n
to 0xFFFF.
29.2.3
PIT Count Register (PCNTR
n
)
The 16-bit, read-only PCNTR
n
contains the counter value. Reading the 16-bit counter with two 8-bit reads
is not guaranteed coherent. Writing to PCNTR
n
has no effect, and write cycles are terminated normally.
1
RLD
Reload bit. The read/write reload bit enables loading the value of PMR
n
into PIT counter when the count reaches
0x0000.
0 Counter rolls over to 0xFFFF on count of 0x0000
1 Counter reloaded from PMR
n
on count of 0x0000
0
EN
PIT enable bit. Enables PIT operation. When PIT is disabled, counter and prescaler are held in a stopped state. This
bit is read anytime, write anytime.
0 PIT disabled
1 PIT enabled
Address: 0xFC08_0002 (PMR0)
0xFC08_4002 (PMR
1
)
0xFC08_8002 (PMR
2
)
0xFC08_C002 (PMR
3
)
Access: Supervisor
read/write
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
PM
W
Reset
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Figure 29-3. PIT Modulus Register (PMR
n)
Table 29-4. PMR
n
Field Descriptions
Field
Description
15–0
PM
Timer modulus. The value of this register is loaded into the PIT counter when the count reaches zero and the
PCSR
n
[RLD] bit is set. However, if PCSR
n
[OVW] is set, the value written to this field is immediately loaded into the
counter. Reading this field returns the value written.
Table 29-3. PCSR
n
Field Descriptions (continued)
Field
Description
Summary of Contents for MCF54455
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Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
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