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Memory Map/Register Definition
MCF5271 Reference Manual, Rev. 2
Freescale Semiconductor
21-5
21.2.1.2 PIT Modulus Register (PMRn)
The 16-bit read/write PMRn contains the timer modulus value that is loaded into the PIT counter
when the count reaches 0x0000 and the PCSRn[RLD] bit is set.
When the PCSRn[OVW] bit is set, PMRn is transparent, and the value written to PMRn is
immediately loaded into the PIT counter. The prescaler counter is reset anytime a new value is
loaded into the PIT counter and also during reset. Reading the PMRn returns the value written in
the modulus latch. Reset initializes PMRn to 0xFFFF.
21.2.1.3 PIT Count Register (PCNTRn)
The 16-bit, read-only PCNTRn contains the counter value. Reading the 16-bit counter with two
8-bit reads is not guaranteed to be coherent. Writing to PCNTRn has no effect, and write cycles
are terminated normally.
1
RLD
Reload bit. The read/write reload bit enables loading the value of PMRn into the PIT
counter when the count reaches 0x0000.
0 Counter rolls over to 0xFFFF on count of 0x0000
1 Counter reloaded from PMRn on count of 0x0000
0
EN
PIT enable bit. Enables PIT operation. When the PIT is disabled, the counter and prescaler
are held in a stopped state. This bit is read anytime, write anytime.
0 PIT disabled
1 PIT enabled
15
14
13
12
11
10
987
6543210
RPM
W
Reset
1111111111111111
Address
IPSBAR + 0x0015_0002 (PIT0);IPSBAR + 0x0016_0002 (PIT1);
IPSBAR + 0x0017_0002 (PIT2); IPSBAR + 0x0018_0002 (PIT3)
Figure 21-3. PIT Modulus Register (PMRn)
15
14
13
12
11
10
987
6543210
RPC
W
Reset
1111111111111111
Address
IPSBAR + 0x0015_0004 (PIT0), IPSBAR + 0x0016_0004 (PIT1),
IPSBAR + 0x0017_0004 (PIT2), IPSBAR + 0x0018_0004 (PIT3)
Figure 21-4. PIT Count Register (PCNTR)
Table 21-3. PCSRn Field Descriptions (Continued)
Bits
Name
Description