Event Counter Mode - Renesas M16C FAMILY Hardware Manual

Under development
Preliminary specification
Specifications in this manual are tentative and subject to change.
R8C/11 Group

12.1.3 Event Counter Mode

In this mode, the timer counts an external signal fed to INT1/CNTR
Counter Mode Specifications"). Figure 12.6 shows TXMR register in event counter mode.
Table 12.4 Event Counter Mode Specifications
Item
Count source
Count operation
Divide ratio
Count start condition
Count stop condition
Interrupt request
generation timing
INT1/CNTR pin function
0
CNTR pin function
0
Read from timer
Write to timer
Select function
Timer X mode register
b7 b6 b5 b4 b3 b2 b1 b0
0 0 0 0
Notes:
1. The 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 Source" in the Usage Notes Reference Book.
Figure 12.6 TXMR Register in Event Counter Mode
Rev.0.91 2003 Sep 08
External signals fed to CNTR
• Down count
• When the timer underflows, it reloads the reload register contents before continuing
counting
1/(n+1)(m+1) n: set value of PREX register, m: set value of TX register
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 interrupt]
• CNTR input count edges [INT1 interrupt]
0
Count source input
Programmable I/O port
Count value can be read by reading TX register
Same applies to PREX register.
Value written to TX register is written to both reload register and counter.
Same applies to PREX register.
• INT1/CNTR polarity switching function
0
Active edge of count source can be selected with R0EDG.
Symbol
TXMR
1
0
Bit symbol
Bit name
Operation mode
TXMOD0
select bit 0, 1
TXMOD1
INT1/CNTR
R0EDG
switching bit
Timer X count
TXS
start flag
TXOCNT
Must set to "0" in event counter mode
TXMOD2
Must set to "0" in event counter mode
TXEDG
Must set to "0" in event counter mode
Must set to "0" in event counter mode
TXUND
page 75 of 184
Specification
pin (Active edge is selected by program)
0
Address After reset
008B 00
16 16
Function
b1 b0
1 0 : Event counter mode
polarity
0 0 : Rising edge
1
1 : Falling edge
0 : Stops counting
1 : Starts counting
12.1 Timer (Timer X)
pin (See "Table 12.4 Event
0
RW
RW
RW
RW
RW
RW
RW
RW
RW