R8C/13 Group
12.1 Timer (Timer X)
12.1.4 Pulse Width Measurement Mode
In this mode, the timer measures the pulse width of an external signal fed to INT1/CNTR0 pin (See
“Table 12.5 Pulse Width Measurement Mode Specifications”). Figure 12.7 shows the TXMR register
in pulse width measurement mode. Figure 12.8 shows an operation example in pulse width measure-
ment mode.
Table 12.5 Pulse Width Measurement Mode Specifications
Item
Count source
Count operation
Specification
f1, f2, f8, f32
• Down-count
• Continuously counts the selected signal only when the measurement pulse is "H" level,
or conversely only "L" level.
• When the timer underflows, the contents in the reload register is reloaded and the count
is contiuned.
Count start condition
Count stop condition
Interrupt request
Write “1” (count start) to TXS bit in TXMR register
Write “0” (count stop) to TXS bit in TXMR register
• When Timer X underflows [Timer X interruption]
• Rising or falling of CNTR0 input (end of measurement period) [INT1 interrupt]
Measurement pulse input
generation timing
INT1/CNTR0 pin function
CNTR0 pin function
Read from timer
Programmable I/O port
Count value can be read by reading TX register
Same applies to PREX register.
Write to timer
Value written to TX register is written to both reload register and counter.
Same applies to PREX register.
_____
Select function
• INT1/CNTR0 polarity switching function
“H” or “L” level duration can be selected with R0EDG bit as the input pulse measurement
Timer X mode register
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
TXMR
Address
008B16
After reset
0016
1
1
0
0
0
0
RW
RW
Bit symbol
TXMOD0
Function
Bit name
b1 b0
Operation mode
select bit 0, 1
1 1 : Pulse width measurement mode
TXMOD1
R0EDG
RW
RW
[CNTR0]
INT1/CNTR0 polarity
0 : Measures “H” level width
1 : Measures “L” level width
[INT1]
switching bit(1)
0 : Rising edge
1 : Falling edge
0 : Stops counting
1 : Starts counting
Timer X count
start flag
RW
RW
RW
TXS
TXOCNT
Set to "0" in pulse width measurement mode
TXMOD2
Set to "0" in pulse width measurement mode
Set to "0" in pulse width measurement mode
Set to "0" in pulse width measurement mode
TXEDG
TXUND
RW
RW
NOTES:
1. IThe IR bit in the INT1IC register may be set to “1” (interrupt requested) when the R0EDG bit is rewritten.
Refer to the paragraph 19.2.5 “Changing Interrupt Factor” in the Usage Notes Reference Book.
Figure 12.7 TXMR Register in Pulse Width Measurement Mode
Rev.1.20 Jan 27, 2006 page 76 of 205
REJ09B0111-0120
RENESAS [ RENESAS TECHNOLOGY CORP ]
