Operation As External Event Counter - Renesas RL78/G1P Hardware User Manual

RL78/G1P

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)
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
TNFENmn
Noise
TImn pin
filter
Remark m: Unit number (m = 0), n: Channel number (n = 0 to 3)
R01UH0895EJ0100 Rev.1.00
Nov 29, 2019
NFEN1
Edge
register detection
TSmn
CHAPTER 6 TIMER ARRAY UNIT
Timer counter
register mn (TCRmn)
Timer data
register mn (TDRmn)
Interrupt
Interrupt signal
controller
(INTTMmn)
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