17.2 Burst Transmission and Echo Reception Pinouts
Table 17-1. Burst Transmission Pinout
Table 17-2. Echo Reception Pinout
Table 17-3. Voltage Reference Pinout
17.3 Echo Burst Transmission and Burst Echo Reception Registers
17.3.1 Burst Pulse-Width High Control Register (BPH)
Register Description: Burst Pulse-Width High Control Register
Register Name: BPH
Register Address: Module 05h, Index 00h
Bit 15: Burst Start (BSTT).
Setting this bit to 1 starts a burst transmission with frequency, duty cycle, and number of pulses deter-
mined by BDIV, BPH, and BCNT. This bit remains 1 until the burst transmission has completed, at which point it is automatically reset
to 0. Changing BSTT to 0 in software is blocked by hardware.
__________________________________________________________________________________________________________ 17-6
MAXQ7667 User’s Guide
B U RST
TRA NS MISSION
SIGNA L
PIN FUN CTION
BURST 45
Burst Output. Provi des trans mit pulses to ultrasonic transducer. Output polar ity is p rog ram mab le. Powers up in
three-state mode.
FILT 26 Filter p in for burst frequency phase- locked loop ( PLL).
ECHO RECEPTION
SIGNA L
PIN FUN CTION
ECHO P 30 Pos itive Echo Input. Capacitively coupled from ultrasonic transducer.
ECHO N 29 Negative Echo Input. Capacitively coupled from ultrasonic trans ducer.
VOLTAGE
REFERENCE
PIN FUN CTION
REFBG 35 Internal 2.5V Reference Output. Connect a m inimum v alue of 0.47µF bypass capacitor to AGND.
REF 34
ADC Reference Input and Reference Buffer Output. This pin is for the ADC reference input. The buffer connected to
the REFBG pin must be disabled to allow the pin to accept an external reference input. Provide a by pass to AGND
w ith a 0.47µF capacitor. This pin requires a low ESR. This can be done by using two capacitors in parallel instead of
one, e.g., a 1µF capacitor in parallel w ith a 10nF capacitor instead of just a 1µF capacitor.
r = read, w = write
Note: BPH is cleared to 0000h on all forms of reset.
Bit #
15 14 13 12 11 10 98
Name BSTT BDS — — — — BPH9 BPH8
Reset 0 0 0 0 0 0 0 0
Access rw rw rrrrrw rw
Bit #
76543210
Name BPH7 BPH6 BPH5 BPH4 BPH3 BPH2 BPH1 BPH0
Reset 0 0 0 0 0 0 0 0
Access rw rw rw rw r w rw rw rw
(114 Seiten)
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