2 timer b mode: capture mode, 7 .1 .2 timer b mode: capture mode -3, Maxq610 user’s guide – Maxim Integrated MAXQ610 User Manual

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MAXQ610 User’s Guide

7.1.2 Timer B Mode: Capture Mode

The 16-bit capture mode is invoked by setting the CP/RLB (TBCN .0) bit to 1 . Timer B, when initially enabled, begins
counting from the TBV value and upon overflow, subsequently continues counting from 0000h to the 0FFFFh overflow,
i .e ., rolls over from 0FFFFh to 0000h if left enabled and running . When an overflow occurs, it sets the TFB Flag . This
flag can generate an interrupt if enabled . The optional capture function is enabled by setting the EXENB (TBCN .3) bit
to 1 . Once this has been done, a 1-to-0-transition on the TBB pin causes the value in Timer B (TBV) to be transferred
into the capture register (TBR) and the EXFB (TBCN .6) flag to be set . Note that the EXFB flag can be set independent
of the state of the TRB bit (e .g ., EXFB can still be set on detection of a negative edge when TRB = 0) . Setting of the
EXFB flag can generate an interrupt if enabled . If the EXENB bit is set to 0, then 1-to-0-transitions on the TBB pin do
not automatically trigger a capture event .

Figure 7-1. Timer B Autoreload Mode

Figure 7-2. Timer B Capture Mode

EXFB

TFB

TIMER B

INTERRUPT

FALLING

EDGE

TBB PIN

EXENB

TBR

0000h

TBV

TBA PIN

TRB

SYSTEM

CLOCK

PRESCALER

TBPS[2:0]

C/TB