Event Counter Mode - Renesas M16C Series Hardware Manual

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
T i m e r X m o d e r e g i s t e r
b 7 b 6 b 5 b 4 b 3 b 2 b 1 b 0
0 0 0 0
N O T E S :
1 . T h e I R b i t i n t h e I N T 1 I C r e g i s t e r m a y b e s e t t o " 1 " ( i n t e r r u p t r e q u e s t e d ) w h e n t h e R 0 E D G b i t i s r e w r i t t e n .
R e f e r t o t h e p a r a g r a p h 1 9 . 2 . 5 " C h a n g i n g I n t e r r u p t F a c t o r " i n t h e U s a g e N o t e s R e f e r e n c e B o o k .
Figure 12.6 TXMR Register in Event Counter Mode
Rev.1.20 Jan 27, 2006
REJ09B0062-0120
External signals fed to CNTR
• Down count
• When the timer underflows, the contents in the reload register is reloaded and the count
is continued.
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]
Count source input (INT1 interrupt 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.
S y m b o l
T X M R
1
0
B i t s y m b o l
Bit name
T X M O D 0 O p e r a t i o n m o d e
s e l e c t b i t 0 , 1
T X M O D 1
I N T 1 / C N T R
R 0 E D G
s w i t c h i n g b i t
T i m e r X c o u n t
T X S
s t a r t f l a g
T X O C N T S e t t o " 0 " i n e v e n t c o u n t e r m o d e
T X M O D 2
S e t t o " 0 " i n e v e n t c o u n t e r m o d e
T X E D G
S e t t o " 0 " i n e v e n t c o u n t e r m o d e
S e t t o " 0 " i n e v e n t c o u n t e r m o d e
T X U N D
page 75 of 204
Specification
pin (Active edge is selected by program)
0
_______
A d d r e s s A f t e r r e s e t
0 0 8 B 0 0
1 6
b1 b0
1 0 : Event counter mode
p o l a r i t y
0 0 : R i s i n g e d g e
(1 )
1 : F a l l i n g e d g e
0 : S t o p s c o u n t i n g
1 : S t a r t s c o u n t i n g
12.1 Timer (Timer X)
pin (See "Table 12.4 Event
0
1 6
F u n c t i o n RW
R W
R W
RW
R W
R W
R W
R W
R W