Datasheet

V850ES/JG3 CHAPTRER 7 16-BIT TIMER/EVENT COUNTER P (TMP)
R01UH0015EJ0300 Rev.3.00 Page 261 of 870
Sep 30, 2010
(c) Processing of overflow when two capture registers are used
Care must be exercised in processing the overflow flag when two capture registers are used. First, an example
of incorrect processing is shown below.
Example of incorrect processing when two capture registers are used
FFFFH
16-bit counter
0000H
TPnCE bit
TIPn0 pin input
TPnCCR0 register
TIPn1 pin input
TPnCCR1 register
INTTPnOV signal
TPnOVF bit
D 00
D 01
D 10
D 11
D 10
<1> <2> <3> <4>
D 00
D 11
D 01
The following problem may occur when two pulse widths are measured in the free-running timer mode.
<1> Read the TPnCCR0 register (setting of the default value of the TIPn0 pin input).
<2> Read the TPnCCR1 register (setting of the default value of the TIPn1 pin input).
<3> Read the TPnCCR0 register.
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
01 − D00).
<4> Read the TPnCCR1 register.
Read the overflow flag. Because the flag is cleared in <3>, 0 is read.
Because the overflow flag is 0, the pulse width can be calculated by (D
11 − D10) (incorrect).
When two capture registers are used, and if the overflow flag is cleared to 0 by one capture register, the other
capture register may not obtain the correct pulse width.
Use software when using two capture registers. An example of how to use software is shown below.