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Timers
16-Bit Timer Setup Examples
When TM4MD[1:0] = b'10' (dur-
ing capture), TM4CA and
TM4CB become read-only regis-
ters. To write to TM4CA or
TM4CB, you must first set
TM4MD[1:0] = b'00'.
Ignore the flags when calculat-
ing the signal width, even when
TM3CA is the larger value.
MN102H75K/F75K/85K/F85K LSI User Manual
change any other operating modes during this step.
3.
Set TM4NLD and TM4EN to 1. This starts the timer. Counting begins at the
start of the next cycle.
To enable timer 4 capture B interrupts:
Cancel all existing interrupt requests. Next, set the interrupt priority level in the
TM4CBLV[2:0] bits of the TM4CBICH register (levels 0 to 6), set the TM4BIE
bit to 1, and set the TM4BIR bit of TM4CBICL to 0. From this point on, an
interrupt request is generated whenever a timer 4 capture B event occurs.
To service the interrupts and calculate the signal width:
1.
Run the interrupt service routine. The routine must determine the interrupt
group, then clear the interrupt request flag.
2.
Calculate the number of cycles the TM4IA signal stays high. Save the con-
tents of TM4CA and TM4CB to the data registers, then subtract the contents
of TM4CA from the contents of TM4CB. Since TM4LP is set to 0, the dif-
ference will be the correct value even if TM4CA is greater than TM4CB.
Timer 4 can input a single-phase capture signal. You must select up counting.
Timer 4 does not operate in STOP mode, when B
clock, it must be synchronized to B
TM4CA captures the count on the rising edge of TM4IA, and TM4CB captures
the count on the falling edge of TM4IA. A timer 4 capture B interrupt occurs
when TM4CB captures the count, and the contents of TM4CA and TM4CB are
read during the interrupt service routine.
In the example timing chart shown in figure 4-36, x'000A' – x'0007' = x'0003',
or 3 cycles. The calculation is correct even when TM4CA is the larger value. The
flags are ignored, so for instance, x'0003' – x'FFFE' = x'0005'.
TM4EN
TM4BC
0
0
1
2
3
B
/4
OSC
TM4CA
0
TM4CB
0
TM4IA
Interrupt
Figure 4-36 Single-Phase Capture Input Timing (Timer 4)
107
Panasonic
is off. If you use an external
OSC
.
OSC
4
5
6
7
8
9
A
B
A-7=3
B
Panasonic Semiconductor Development Company
C
D
E
F 10 11 12
7
A
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