H838024 datasheet(332/697 Pages) RENESAS

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Section 9 Timers

Rev. 7.00 Mar 10, 2005 page 290 of 652

REJ09B0042-0700

9.5.4

Operation

Timer G is an 8-bit timer with built-in input capture and interval functions.

Timer G Functions

Timer G is an 8-bit up-counter with two functions, an input capture timer function and an interval

timer function.

The operation of these two functions is described below.

a. Input capture timer operation

When the TMIG bit in port mode register 1 (PMR1) is set to 1, timer G functions as an input

capture timer*.

In a reset, timer mode register G (TMG), timer counter G (TCG), input capture register GF

(ICRGF), and input capture register GR (ICRGR) are all initialized to H'00.

Following a reset, TCG starts counting on the

φ/64 internal clock.

The input clock can be selected from four internal clock sources by bits CKS1 and CKS0 in

TMG.

When a rising edge/falling edge is detected in the input capture signal input from the TMIG

pin, the TCG value at that time is transferred to ICRGR/ICRGF. When the edge selected by

IIEGS in TMG is input, IRRTG in IRR2 is set to 1, and if the IENTG bit in IENR2 is 1 at this

time, an interrupt request is sent to the CPU. For details of the interrupt, see section 3.3,

Interrupts.

TCG can be cleared by a rising edge, falling edge, or both edges of the input capture signal,

according to the setting of bits CCLR1 and CCLR0 in TMG. If TCG overflows when the

input capture signal is high, the OVFH bit in TMG is set; if TCG overflows when the input

capture signal is low, the OVFL bit in TMG is set. If the OVIE bit in TMG is 1 when these

bits are set, IRRTG in IRR2 is set to 1, and if the IENTG bit in IENR2 is 1, timer G sends an

interrupt request to the CPU. For details of the interrupt, see section 3.3, Interrupts.

Timer G has a built-in noise canceler that enables high-frequency component noise to be

eliminated from pulses input from the TMIG pin. For details, see section 9.5.3, Noise

Canceler.

Note: * An input capture signal may be generated when TMIG is modified.

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