M-V850E-IA4 Renesas Electronics America, M-V850E-IA4 Datasheet - Page 267

• Manufacturer Part Number: M-V850E-IA4
• Description: KIT EVAL V850E IA4 UPD70F3186
• Manufacturer: Renesas Electronics America

Specifications of M-V850E-IA4

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

(d) Processing of overflow if capture trigger interval is long
If the pulse width is greater than one cycle of the 16-bit counter, care must be exercised because an
overflow may occur more than once from the first capture trigger to the next. First, an example of incorrect
processing is shown below.
The following problem may occur when long pulse width is measured in the free-running timer mode.
<1> Read the TPkCCRa register (setting of the default value of the TIPka pin input).
<2> An overflow occurs. Nothing is done by software.
<3> An overflow occurs a second time. Nothing is done by software.
<4> Read the TPkCCRa register.
Remark
If an overflow occurs twice or more when the capture trigger interval is long, the correct pulse width may
not be obtained.
If the capture trigger interval is long, slow the count clock to lengthen one cycle of the 16-bit counter, or
use software. An example of how to use software is shown next.
TPkCCRa register
INTTPkOV signal
Read the overflow flag. If the overflow flag is 1, clear it to 0.
Because the overflow flag is 1, the pulse width can be calculated by (10000H + D
(incorrect).
Actually, the pulse width must be (20000H + D
TIPka pin input
16-bit counter
TPkOVF bit
Example of incorrect processing when capture trigger interval is long
k = 0, 2
a = 0, 1
TPkCE bit
FFFFH
0000H
CHAPTER 6 16-BIT TIMER/EVENT COUNTER P (TMP)
User’s Manual U16543EJ4V0UD
D
a0
<1> <2>
a1
− D
1 cycle of 16-bit counter
a0
) because an overflow occurs twice.
Pulse width
D
a0
<3> <4>
D
a1
D
a1
a1
− D
a0
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)