Renesas 7700 FAMILY User Manual page 108

(2) Two-phase pulse signal processing function (Timers A2 to A4)
For timers A2 to A4, the two-phase pulse signal processing function is selected by setting the two-
phase pulse signal processing select bits (bits 5 to 7 at address 44
Figure 5.4.6 shows the timer A2, A3, and A4 mode registers when the two-phase pulse signal
processing function is selected.
With timers selecting the two-phase pulse signal processing function, the timer counts two kinds of
pulses of which phases differ by 90 degrees. There are two types of the two-phase pulse signal
processing: normal processing and quadruple processing. In timers A2 and A3, normal processing
is performed; in timer A4, quadruple processing is performed.
For some bits of the port P5 and P6 direction registers correspond to pins used for two-phase pulse
input, set these bits for the input mode.
Fig. 5.4.6 Timer A2, A3, and A4 mode registers when two-phase pulse signal processing function is
selected
Normal processing
The timer up-counts the rising edges to the TAk
TAk pin's input signal level goes from "L" to "H" while the TAk
IN
is "H" level.
The timer down-counts the falling edges to the TAk
the TAk pin's input signal level goes from "H" to "L" while the TAk
IN
(Refer to Figure 5.4.7.)
TAk
TAk
(k=2, 3)
Fig. 5.4.7 Normal processing
b7 b6 b5 b4 b3 b2 b1
0 1 0 0 0 1
: It may be either "0" or "1."
"H"
OUT
"L"
"H"
IN
"L"
Up- Up
count count
+1
7751 Group User's Manual
b0
Timer A2 mode register (Address 58
Timer A3 mode register (Address 59
Timer A4 mode register (Address 5A
pin when the phase has the relationship that the
IN
pin when the phase has the relationship that
IN
Up-
Down-
Up-
count
count
count
+1 +1 –1
TIMER A
5.4 Event counter mode
) to "1." (Refer to Figure 5.4.5.)
16
)
16
)
16
)
16
(k = 2 and 3) pin's input signal
OUT
pin's input signal is "H" level.
OUT
Down- Down-
count count
–1 –1
5–27