Motorola APX 5000 Service Manual page 73

Theory of Operation
: Controller 3-47
Prior to the LCD interpreting any commands, the correct display power-up sequence must be
initiated. First the V_EXT_1.85 (1.875 V) and V_2.775D (2.775 V) supplies must be at 90% or above
threshold and stable for 10us, and then reset can be asserted high. After OMAP de-asserts the reset
out signal (OMAP_RESET) the SLPOUT command can be sent. Now configuration commands are
ready to be sent to the LCD module.
The QVGA LCD module is only intended to operate up to +80°C due to ghosting effects. Therefore
software will shut off the display and backlight if the +80°C limit is reached. The display and backlight
will remain off until temperature drops below +75°C. The temperature sensor, U6401, for the display
cut-off is located near the top display connector and is input into MAKO A/D Channel 3, pin M14.
For enhanced display readability, the default backlight is set to a dim state while the radio is in
Standby mode; however, the backlight turns to full brightness through a button press, call receive,
emergency call, and other status indicators. See Section 3.2.6.3: "Intelligent Lighting" for the display
backlight operation.
3.2.6.2.2 FSTN
All APX 5000/APX 6000/APX 6000XE/SRX 2200 Radios are equipped with a caller ID (CID) top
display. This top display is a 1.1", Transflective, FSTN (Film compensated Super Twisted Nematic)
32 row x 112 column LCD with black pixels on a light background. This display is a component of the
control top sub-assembly with all interconnections passing through control top FPC. The display is
controlled via OMAP's 3 wire SPI interface to program the display driver IC registers and send data/
image information to the display. The active low chip select line, T_DISP_SPI_CS, is sent from the
OMAP GPIO_5 pin P3. The T_DISP_DATA_CMD line indicates whether the data being sent across
the SPI bus is register/command settings or if it's data/image information. The display driver contains
internal GRAM, which stores the current display content information, and the data/image information
is only sent when the display content needs to be updated.
Prior to sending any information to the LCD driver, the proper power-up sequence must be
instantiated. First, the V_EXT_1.85 and V_2.775D voltage supplies must be stable for at least 1 ms.
Next, the active low reset line, T_DISP_RESET, to the LCD driver must see a low pulse of 10 usec or
longer prior to communicating to the LCD driver. Then, the register setting information will be sent to
the display driver, followed by the image/data information.
The top LCD contains various LEDs for multiple backlight color combinations depending upon the
mode of operation. The programmable default backlight setting is off in standby mode, but will
illuminate to max brightness during a button push, call receive, receive mode, low battery, out of
range, emergency, etc. The details of the top display backlight settings are listed in Section 3.2.6.3:
"Intelligent Lighting". The top display contains 2 parallel side firing white LEDs and 2 parallel Red-
Green side firing bi-color LEDs.