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Timer Module
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
15-3
15.3
General-Purpose Timer Registers
The following sections describe the timer registers.
15.3.1
Timer Mode Registers (TMR0–TMR3)
, have fields for choosing a prescaler, a clock edge, and other parameters.
TMR
n
15
8
7
6
5
4
3
2
1
0
Field
PRESCALER (PS)
CE
OM
1
ORI
FRR
CLK
RST
Reset
0000_0000_0000_0000
R/W
Read/Write
Addr
MBAR + 0x200 (TMR0); 0x220 (TMR1); 0x240 (TMR2); 0x260 (TMR3)
1
Not implemented (reserved) in TMR2 and TMR3.
Figure 15-2. Timer Mode Registers (TMR0–TMR3)
Table 15-1. TMR
n
Field Descriptions
Bits
Name
Description
15–8
PS
Prescaler. Programmed to divide the clock input by values from 1 to 256. The value 0000_0000 divides the
clock by 1; the value 1111_1111 divides the clock by 256.
7–6
CE
Capture edge and enable interrupt.
00 Disable capture and interrupt on capture event
01 Capture on rising edge only and generate interrupt on capture event
10 Capture on falling edge only and generate interrupt on capture event
11 Capture on any edge and generate interrupt on capture event
5
OM
Output mode (TMR0 and TMR1 only. Reserved in TMR2 and TMR3)
0 Active-low pulse for one system clock cycle (15 nS at 66 MHz)
1 Toggle output
TOUT
n
is high at reset but is unavailable externally until the appropriate port control register is configured for
this function. See
Section 17.2, “Port Control Registers
.”
4
ORI
Output reference interrupt enable
0 Disable interrupt for reference reached (does not affect interrupt on capture function)
1 Enable interrupt upon reaching the reference value If ORI is 1 when the TER[REF] is set, an immediate
interrupt occurs.
3
FRR Free
run/restart
0 Free run. Timer count continues to increment after the reference value is reached.
1 Restart. Timer count is reset immediately after the reference value is reached.
2–1
CLK
Input clock source for the timer
00 Stop count
01 Master system clock
10 Master system clock divided by 16. TIN0 and TIN1 are external to the MCF5272 and are not synchronized
to the system clock, so successive timeout lengths may vary slightly.
11 Corresponding TIN pin, TIN0 or TIN1 (falling edge), unused in TMR2 and TMR3
The minimum high and low periods for TIN as the clock source is 1 system clock, which gives a maximum TIN
frequency of clock/2.
Содержание MCF5272 ColdFire
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