TMP89FS60 datasheet(166/410 Pages) TOSHIBA

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Page 152

13. 16-bit Timer Counter (TCA)

13.4 Timer Function

TMP89FS60

RA001

13.4.2 External trigger timer mode

In the external trigger timer mode, the up counter starts counting when it is triggered by the input to the

TCA0 pin.

13.4.2.1 Setting

Setting the operation mode selection TA0MOD<TA0M> to "100" activates the external trigger timer

mode. Select the source clock at TA0MOD<TA0CK>.

Select the trigger edge at the trigger edge input selection TA0MOD<TA0TED>. Setting

TA0MOD<TA0TED> to "0" selects the rising edge, and setting it to "1" selects the falling edge.

Note that this mode uses the TA0 input pin, and the TCA0 pin must be set to the input mode beforehand

in port settings.

The operation is started by setting TA0CR<TA0S> to "1". After the timer is started, writing to

TA0MOD and TA0CR<TA0OVE> is disabled. Be sure to complete the required mode settings before

starting the timer.

13.4.2.2 Operation

After the timer is started, when the selected trigger edge is input to the TCA0 pin, the up counter incre-

ments according to the selected source clock. When a match between the up counter value and the value

set to timer register A (TA0DRA) is detected, an INTTA0 interrupt request is generated and the up counter

is cleared to "0000H". After being cleared, the up counter continues counting.

When TA0MOD<TA0METT> is "1" and the edge opposite to the selected trigger edge is detected, the

up counter stops counting and is cleared to "0000H". Subsequently, when the selected trigger edge is

detected, the up counter restarts counting. In this mode, an interrupt request can be generated by detecting

that the input pulse exceeds a certain pulse width. If TA0MOD<TA0METT> is "0", the detection of the

selected edge and the opposite edge is ignored during the period from the detection of the specified trigger

edge and the start of counting through until the match detection.

Setting TA0CR<TA0S> to "0" during the timer operation causes the up counter to stop counting and be

TMP89FS60 Datasheet(PDF) 166 Page - Toshiba Semiconductor