Guest
When reading the datasheet of the picmicro microchip there are
some terms I don't understand. What is tristate. Also, what is
brown-out-detect?
Tia
some terms I don't understand. What is tristate. Also, what is
brown-out-detect?
Tia
Navigation
Install the app
How to install the app on iOS
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
More options
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
H
Howard Henry Schlunder
Guest
A pin can be configured to output a high signal (pull towards Vdd), output a
low signal (pull towards Vss), or it could be configured as an input (let
the pin float in high impedance mode). A tristated pin means that it is
configured as an input. Once it's understood that tristate and input are
synonymous, the TRISA, TRISB, etc. register names and how the bits work seem
quite logical.
The brown-out-detect module measures the voltage of Vdd and when it drops
too low (somewhere around 3V I think for PIC12F and PIC16F series), it will
place the chip in reset. In other words, when the power supply starts
sagging, it will detect the condition, stop executing code, tristate all the
pins, and reset the program counter. When the voltage climbs back above a
certain threshold, the PIC restarts executing code (but from the beginning
since the program counter was cleared). The brown-out-detect module can be
useful if you are switching power MOSFETs or something which would explode
if you gave it a prolonged gate drive of only 3V or less.
Howard Henry Schlunder
<anon7890@btinternet.com> wrote in message
news:bhg24f$qbi$1@sparta.btinternet.com...
low signal (pull towards Vss), or it could be configured as an input (let
the pin float in high impedance mode). A tristated pin means that it is
configured as an input. Once it's understood that tristate and input are
synonymous, the TRISA, TRISB, etc. register names and how the bits work seem
quite logical.
The brown-out-detect module measures the voltage of Vdd and when it drops
too low (somewhere around 3V I think for PIC12F and PIC16F series), it will
place the chip in reset. In other words, when the power supply starts
sagging, it will detect the condition, stop executing code, tristate all the
pins, and reset the program counter. When the voltage climbs back above a
certain threshold, the PIC restarts executing code (but from the beginning
since the program counter was cleared). The brown-out-detect module can be
useful if you are switching power MOSFETs or something which would explode
if you gave it a prolonged gate drive of only 3V or less.
Howard Henry Schlunder
<anon7890@btinternet.com> wrote in message
news:bhg24f$qbi$1@sparta.btinternet.com...
When reading the datasheet of the picmicro microchip there are
some terms I don't understand. What is tristate. Also, what is
brown-out-detect?
Tia
G
grahamk
Guest
anon7890@btinternet.com wrote:
--
Have a look at http://homepage.ntlworld.com/g.knott/elect357.htm
--When reading the datasheet of the picmicro microchip there are
some terms I don't understand. What is tristate. Also, what is
brown-out-detect?
Tia
--
Have a look at http://homepage.ntlworld.com/g.knott/elect357.htm
Guest
thanks to all
"grahamk" <g.knott@ntlworld.com> wrote in message news:TZP_a.12511$yl6.1481@newsfep4-winn.server.ntli.net...
anon7890@btinternet.com wrote:
--
Have a look at http://homepage.ntlworld.com/g.knott/elect357.htm
"grahamk" <g.knott@ntlworld.com> wrote in message news:TZP_a.12511$yl6.1481@newsfep4-winn.server.ntli.net...
anon7890@btinternet.com wrote:
--When reading the datasheet of the picmicro microchip there are
some terms I don't understand. What is tristate. Also, what is
brown-out-detect?
Tia
--
Have a look at http://homepage.ntlworld.com/g.knott/elect357.htm
G
GGPP
Guest
Tristate means that the output can have 3 dif. states : high (V+), low(Gnd)
and high-impedance.
I do not know what brown-out-detect is.
Gerard.
<anon7890@btinternet.com> wrote in message
news:bhg24f$qbi$1@sparta.btinternet.com...
and high-impedance.
I do not know what brown-out-detect is.
Gerard.
<anon7890@btinternet.com> wrote in message
news:bhg24f$qbi$1@sparta.btinternet.com...
When reading the datasheet of the picmicro microchip there are
some terms I don't understand. What is tristate. Also, what is
brown-out-detect?
Tia
J
Jim Large
Guest
Howard Henry Schlunder wrote:
They can drive a bus high, drive it low, or not drive
it at all; but they can't sense the bus.
Maybe you don't see so many of these anymore now that
everything's microcontrollers and programmable logic,
but it was pretty common back in the days of MSI logic.
-- JmL
Not always. Some tristate-able pins are just outputs.A pin can be configured to output a high signal (pull
towards Vdd), output a low signal (pull towards Vss),
or it could be configured as an input (let the pin
float in high impedance mode). A tristated pin means
that it is configured as an input.
They can drive a bus high, drive it low, or not drive
it at all; but they can't sense the bus.
Maybe you don't see so many of these anymore now that
everything's microcontrollers and programmable logic,
but it was pretty common back in the days of MSI logic.
-- JmL
R
Robert Monsen
Guest
brown out detect detects a drop in voltage between the positive supply and
ground, and usually resets the chip or something like that..
Tristate outputs are used in computer systems built from discrete logic for
busses. You activate the chip using address lines, and all other chips on
the bus that are not selected present high impedance (ie, the 'third' state)
instead of a logic 0 or 1. That way, multiple devices can coexist on the bus
without interfering with one another.
In PIC land, if you configure a pin to be 'tristate' (using the TRISTA
register), its an input rather than an output, and the output drivers are
disconnected from the pin. This is a bit different from the original
meaning...
Regards,
Bob Monsen
"GGPP" <fa304730@skynet.be> wrote in message
news:3f3bff9f$0$888$ba620e4c@reader1.news.skynet.be...
ground, and usually resets the chip or something like that..
Tristate outputs are used in computer systems built from discrete logic for
busses. You activate the chip using address lines, and all other chips on
the bus that are not selected present high impedance (ie, the 'third' state)
instead of a logic 0 or 1. That way, multiple devices can coexist on the bus
without interfering with one another.
In PIC land, if you configure a pin to be 'tristate' (using the TRISTA
register), its an input rather than an output, and the output drivers are
disconnected from the pin. This is a bit different from the original
meaning...
Regards,
Bob Monsen
"GGPP" <fa304730@skynet.be> wrote in message
news:3f3bff9f$0$888$ba620e4c@reader1.news.skynet.be...
Tristate means that the output can have 3 dif. states : high (V+),
low(Gnd)
and high-impedance.
I do not know what brown-out-detect is.
Gerard.
anon7890@btinternet.com> wrote in message
news:bhg24f$qbi$1@sparta.btinternet.com...
When reading the datasheet of the picmicro microchip there are
some terms I don't understand. What is tristate. Also, what is
brown-out-detect?
Tia