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MAXQ7667 User’s Guide

6.7.9.2 Measure High-Pulse Duration Repeatedly

To measure the duration of high pulses seen on the T2P0 input pin repeatedly, the Type 2 timer is configured for a single-shot delayed

run, gating enabled for logic low, capture on the falling edge. The CPRL2 bit can be set to generate a reload on each falling edge.

;

------------------ Reset State: T2R0 = T2V0 = T2C0 = 0000h ------------------------

MOVE T2CFG0, #00000100b ; T2CI =0 (sysclk/N input)

; T2DIV2:0 =000 (/1)

; T2MD =0 (16-bit)

; CCF1:0 =10 (falling edge)

; C/T2 =0 (timer/capture)

MOVE T2CNA0, #10001111b ; ET2 =1 (enable Type 2 Timer ints)

; T2OE0 =0 (input)

; T2POL0 =0 (gating level = ‘0’)

; TR2L:TR2 =01 (start timer on single shot

; condition)

; CPRL2 =1 (reload on capture edge)

; SS2 =1 (single shot mode)

; G2EN =1 (gating enabled)

; ------------------ TCC2 Interrupt : DURATION = T2C0

EVENTS:

1A: FALLING EDGE CAUSES CAPTURE/RELOAD; SINGLE-SHOT CAPTURE CYCLE BEGINS; TIMER CLOCK GATED SINCE T2P0 PIN = 0.

2A: GATING CONDITION REMOVED; TIMER RUNS.

3A: FALLING EDGE CAUSES CAPTURE/RELOAD; SINGLE-SHOT CAPTURE CYCLE ENDS; DURATION = T2C0. TIMER CONTINUES TO OPERATE

SINCE TR2 = 1, BUT TIMER CLOCK GATED SINCE T2P0 PIN = 0.

4A: GATING CONDITION REMOVED; TIMER RUNS.

1B: GATING CONDITION REMOVED; SINGLE-SHOT CAPTURE CYCLE BEGINS.

2B: FALLING EDGE CAUSES CAPTURE/RELOAD; SINGLE-SHOT CAPTURE CYCLE ENDS; DURATION = T2C0. TIMER CONTINUES TO OPERATE

SINCE TR2 = 1, BUT TIMER CLOCK GATED SINCE T2P0 PIN = 0.

3B: GATING CONDITION REMOVED; TIMER RUNS.

T2P0 PIN

CODE EXECUTION:

POINT A

CODE EXECUTION:

POINT B

Figur

e 6-9. T

ype 2 T

imer Application Example—Measur

e High Pulse W

idth

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Maxim-integrated MAXQ7667 Bedienungsanleitung Seite 122