ST72774/ST727754/ST72734
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16-BIT TIMER (Cont’d)
CONTROL REGISTER 2 (CR2)
Read/Write
Reset Value: 0000 0000 (00h)
Bit 7 = OC1E
Output Compare 1 Enable.
0: Output Compare 1 function is enabled, but
the OCMP1 pin is a general I/O.
1: Output Compare 1 function is enabled, the
OCMP1 pin is dedicated to the Output Com-
pare 1 capability of the timer.
Bit 6 = OC2E
Output Compare 2 Enable.
0: Output Compare 2 function is enabled, but
the OCMP2 pin is a general I/O.
1: Output Compare 2 function is enabled, the
OCMP2 pin is dedicated to the Output Com-
pare 2 capability of the timer.
Bit 5 = OPM
One Pulse Mode.
0: One Pulse Mode is not active.
1: One Pulse Mode is active, the ICAP1 pin can
be used to trigger one pulse on the OCMP1
pin; the active transition is given by the
IEDG1 bit. The length of the generated pulse
depends on the contents of the OC1R regis-
ter.
Bit 4 = PWM
Pulse Width Modulation.
0: PWM mode is not active.
1: PWM mode is active, the OCMP1 pin outputs
a programmable cyclic signal; the length of
the pulse depends on the value of OC1R reg-
ister; the period depends on the value of
OC2R register.
Bit 3, 2 = CC1-CC0
Clock Control.
The value of the timer clock depends on these bits:
Table 15. Clock Control Bits
Bit 1 = IEDG2
Input Edge 2.
This bit determines which type of level transition on
the ICAP2 pin will trigger the capture.
0: A falling edge triggers the capture.
1: A rising edge triggers the capture.
Bit 0 = EXEDG
External Clock Edge.
This bit determines which type of level transition on
the external clock pin EXTCLK will trigger the free
running counter.
0: A falling edge triggers the free running coun-
ter.
1: A rising edge triggers the free running coun-
ter.
70
OC1E OC2E OPM PWM CC1 CC0 IEDG2 EXEDG
CC1
CC0
Timer Clock
00
fCPU / 4
01
fCPU / 2
10
fCPU / 8
11
External Clock (where
available)