Maxim-integrated MAXQ622 Bedienungsanleitung PDF herunterladen (Seite 117)

MAXQ612/MAXQ622 User’s Guide

Maxim Integrated 7-3

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

150

FALLING

EDGE

TBB PIN

EXENB

TBR

0000h

TBV

TBA PIN

TRB

SYSTEM

CLOCK

PRESCALER

TBPS[2:0]

C/TB