Pulse Width Measurement Mode - Toshiba TLCS-870/C Series Manual

8.3.3 Pulse Width Measurement mode

In this mode, pulse widths are counted on the falling edge of logical AND-ed pulse between ECIN pin input
(window pulse) and the internal clock. When using this mode, set TC1CR1<TC1CK> to suitable internal clock
and then set TC1CR2<SEG> to "0" (Both edges can not be used).
An INTTC1 interrupt is generated when the ECIN input detects the falling edge of the window pulse or both
rising and falling edges of the window pulse, that can be selected by TC1CR2<SGEDG>.
The contents of TREG1A should be read while the count is stopped (ECIN pin is low), then clear the counter
using TC1CR1<TC1C> (Normally, execute these process in the interrupt program).
When the counter is not cleared by TC1CR1<TC1C>, counting-up resumes from previous stopping value.
When up counter is counted up from 3FFFFH to 00000H, an overflow occurs. At that time, TC1SR<HEOVF>
is set to "1". TC1SR<HEOVF> remains the previous data until the counter is required to be cleared by
TC1CR1<TC1C>.
Note:In pulse width measurement mode, if TC1CR1<TC1S> is written to "00" while ECIN input is "1", INTTC1 inter-
rupt occurs. According to the following step, when timer counter is stopped, INTTC1 interrupt latch should be
cleared to "0".
Example :
TC1STOP :
Note 1: When SGEDG (window gate pulse interrupt edge select) is set to both edges and ECIN pin input is "1" in
the pulse width measurement mode, an INTTC1 interrupt is generated by setting TC1S (TC1 start control)
to "10" (start).
Note 2: In the pulse width measurement mode, HECF (operating status monitor) cannot used.
Note 3: Because the up counter is counted on the falling edge of logical AND-ed pulse (between ECIN pin input and
the internal clock), if ECIN input becomes falling edge while internal source clock is "H" level, the up
counter stops plus "1".
ECIN pin input
Internal clock
AND-ed pulse
(Internal signal)
Up counter
INTTC1 interrupt
TC1CR1<TC1C>
Figure 8-4 Pulse width measurement mode timing chart
¦ ¦
DI
CLR (EIRH). 0
LD (TC1CR1), 00011010B
LD (ILH), 11111110B
SET (EIRH). 0
EI
¦ ¦
Count Start
0 1 2 3
; Clear IMF
; Clear bit0 of EIRH
; Stop timer couter 1
; Clear bit0 of ILH
; Set bit0 of EIRH
; Set IMF
Count Stop
n-2 n-1 n n+1
Read Clear
Interrupt
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TMP86PM29BUG
Count Start
0 1 2