Texas Instruments C28 Series Student Guide

Capture Units
Some Uses for the Capture Units
Some Uses for the Capture Units
♦ Synchronized ADC start with capture event
Problem: At low speeds, calculation of
speed based on a measured position
change at fixed time intervals produces
large estimate errors
Alternative: Estimate the speed using a measured time
interval at fixed position intervals
Signal from one
quadrature
encoder channel
♦ Low speed velocity estimation from incr. encoder:
♦ Measure the time width of a pulse
v
k
≈
∆x
t
k
-t
k-1
v
k
≈
∆t
x
k
-x
k-1
∆x
Capture Units Block Diagram
Capture Units Block Diagram
(EVA)
(EVA)
Can latch on:
• rising edge
• falling edge
• both
GP Timer 1
Counter
T1CNT . 15 - 0
Edge
Detect
CAP3TOADC
CAP1,2,3
MUX
GP Timer 2
Counter
T2CNT . 15 - 0
CAPCONA . 10 - 9
Enable
CAPCONA . 14 -12
2-Level Deep
FIFO
/
3
.
CAPCONA . 8
Edge Select
CAPCONA . 7 - 2
CAPCONA . 15
CAPRESET
ADC Start
(CAP 3)
CAPFIFOA . 13 - 8
CAPxFIFO Status
RS
7 - 28 C28x - Event Manager

Texas Instruments C28 Series Specifications

General

Brand	Texas Instruments
Model	C28 Series
Category	Computer Hardware
Language	English