Owner's manual

MAXQ7665/MAXQ7666 User’s Guide

7-26

7.4.5 Overflow/Interrupt on Cumulative Time

To cause an overflow only when the T0 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 T0 input low for (10000h-01234h) T2CLKs

MOVE T2CFG0, #01110000b ;

; T2DIV[2:0] =111 (/128)

; T2MD =0 (16-bit)

; CCF[1:0] =00 (no edges)

; C/T2 =0 (timer/compare)

MOVE T2CNA0, #10101001b ; ET2 =1 (enable 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

T0 PIN

CODE EXECUTION:

POINT A

CODE EXECUTION:

POINT B

EVENTS:

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

2A: TIMER OVERFLOWS.

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

Figure 7-10. Type 2 Timer Application Example—Overflow/Interrupt on Cumulative Time

Maxim Integrated