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RL78/G1A CHAPTER 6 TIMER ARRAY UNIT
R01UH0305EJ0200 Rev.2.00 247
Jul 04, 2013
6.8.2 Operation as external event counter
The timer array unit can be used as an external event counter that counts the number of times the valid input edge
(external event) is detected in the TImn pin. When a specified count value is reached, the event counter generates an
interrupt. The specified number of counts can be calculated by the following expression.
Specified number of counts = Set value of TDRmn + 1
Timer count register mn (TCRmn) operates as a down counter in the event counter mode.
The TCRmn register loads the value of timer data register mn (TDRmn) by setting any channel start trigger bit (TSmn,
TSHm1, TSHm3) of timer channel start register m (TSm) to 1.
The TCRmn register counts down each time the valid input edge of the TImn pin has been detected. When TCRmn =
0000H, the TCRmn register loads the value of the TDRmn register again, and outputs INTTMmn.
After that, the above operation is repeated.
An irregular waveform that depends on external events is output from the TOmn pin. Stop the output by setting the
TOEmn bit of timer output enable register m (TOEm) to 0.
The TDRmn register can be rewritten at any time. The new value of the TDRmn register becomes valid during the next
count period.
Figure 6-45. Block Diagram of Operation as External Event Counter
Edge
detection
TImn pin
Clock selection
Trigger selection
TSmn
Interrupt signal
(INTTMmn)
Interrupt
controller
Timer counter
register mn (TCRmn)
Timer data
register mn (TDRmn)
Noise
filter
TNFENxx
Remark m: Unit number (m = 0), n: Channel number (n = 0 to 7 (however, timer input pin (TImn), timer output pin
(TOmn) : n = 0, 1, 3 to 7))