mwebsurfer wrote:
> Do lcd monitors scan like crt monitors or tv's? Any help will be
> appreciated.
The interface to the panel "scans" or is "in scan order".
The actual method used to charge thin film transistor switched
cells, is unstated in the datasheets. In principle, in terms of
the available interconnect, you could charge a row of elements
at a time, which means visiting all the columns within a frame time.
The other detail, is the voltage across a cell must be A.C.
(alternating current) only, and no net DC is allowed across
a cell. I don't know if that means the cells have to be charged
to V+ and to V- per frame time, or how they arrange that. One of
the documents below, implies that. The trouble with documents like
this, is figuring out whether they represent current technique.
http://www.arcom.com/products/icp/dev_kits/NEC_TFT_Nov06.pdf
The description here says they activate a row and charge an
entire column.
http://en.wikipedia.org/wiki/LCD
"Each pixel has its own dedicated transistor, allowing each column
line to access one pixel. When a row line is activated, all of the
column lines are connected to a row of pixels and the correct voltage
is driven onto all of the column lines. The row line is then deactivated
and the next row line is activated. All of the row lines are activated
in sequence during a refresh operation."
"Multiplex driving method"
http://www2.okisemi.com/site/faq/displaydriverfaqs/lcdfaq/lcd10
(Shows some multiplexed waveforms, more complicated than expected)
http://www.freescale.com/files/microcontrollers/doc/app_note/AN3219.pdf
(Some parts apparently used on LCD monitors. Source driver and Gate
driver, perhaps corresponding to frontplane and backplane described in
the other document. Another surprise - the gate drive chip has a huge
voltage rating of up to 45 volts. I wonder what tech that uses ?)
http://www.okisemi.com/en/392/display/000416.html
So at the very least, a line of "scan order" pixels would have to be stored,
to allow driving a line of cells. I don't know what the "odd" and "even"
implies - on the one hand, it looks like it is providing the necessary
A.C. characteristic to the net cell voltage (no DC allowed), but also implies
that the entire pixmap would have to be stored.
The cells have such a long discharge period, that you should not be able
to see anything of the charging method.
While by now, you probably hate my reading assignments, this article discusses
some of the most recent tricks in LCD monitor design.
http://www.xbitlabs.com/articles/other/display/lcd-parameters.html
This page, for example, describes the differences between CRT phosphor
response, and what the LCD cell does.
http://www.xbitlabs.com/articles/other/display/lcd-parameters_3.html
HTH,
Paul