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MAXQ7667 User’s Guide

6.7.9.5 Overflow/Interrupt on Cumulative Time

To cause an overflow only when the T2P0 pin has been low for some cumulative duration, the Type 2 timer can be configured to the

gated compare mode of operation with an initial starting value appropriate for the cumulative duration to be detected.

;

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

MOVE T2V0, #1234h ; Overflow after T2P0 input low for (10000h-01234h) CLKs

MOVE T2CFG0, #01110000b ; T2CI =0 (sysclk/N input)

; T2DIV2:0 =111 (/128)

; T2MD =0 (16-bit)

; CCF1:0 =00 (no edges)

; C/T2 =0 (timer/compare)

MOVE T2CNA0, #10101001b ; ET2 =1 (enable Type 2 Timer ints)

; T2OE0 =0 (input)

; T2POL0 =1 (gating level = ‘1’)

; TR2L:TR2 =01 (start timer)

; CPRL2 =0 (no capture possible)

; SS2 =0 (not single shot mode)

; G2EN =1 (gating enabled)

; ------------------ TF2 Interrupt : Cumulative low duration reached

T2P0 PIN

CODE EXECUTION:

POINT A

CODE EXECUTION:

POINT B

EVENTS:

1A: GATING CONDITION IS REMOVED; TIMER BEGINS TO RUN.

2A: TIMER 2 OVERFLOWS.

1B–2B: SAME SEQUENCE AS 1A–2A, EXCEPT THAT TIMER 2 STARTS RUNNING IMMEDIATELY SINCE IT IS NOT GATED.

Figure 6-12. Type 2 Timer Application Example—Overflow/Interrupt on Cumulative Time

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Maxim-integrated MAXQ7667 Bedienungsanleitung Seite 125