2192-12132-000-000
The following PXA255 GP lines are used for LCD functions.
PXA255 GP
Function
GP9 Backlight
Enable
GP10
LCD Vcc Enable
GP16 (PWM0)
Backlight brightness control
Backlight Enable
This controls the switched backlight supply voltage. When the GP9 is set to a logic high the
backlight supply is turned on BLKSAFE (PL3 – Pin 2). The BLKEN signal on PL3 (pin 1) is the
un-buffered GP9 signal.
LCD Vcc Enable
This controls the switched LCD supply voltage when the GP10 is set to a logic high the LCD
supply is turned on LCDSAFE (PL3 – Pin 6). The default LCD output supply is 3.3V.
Note
: This may be factory configured (using a surface mount resistor) to 5V.
Backlight Brightness Control
GP16 is available on PL3, pin 7. This can be used in one of two ways, dependant upon the type
of backlight inverter being used. Some inverters have a ‘DIM’ function, a logic level to choose
between two levels of intensity, if this is the case GP16 can be used to set this. Other inverters
have an input suitable for a PWM (Pulse Width Modulation); in this case GP16 can be
configured as PWM0.
Interrupt Assignments
Internal Interrupts
For details on the PXA255 interrupt controller and internal peripheral interrupts please refer to
the Intel PXA255 developer’s manual on the Development Kit CD.
External Interrupts
The following table lists the GP lines used for generating interrupts externally to the PXA255:
PXA255 GP
Peripheral
GP0 Ethernet
GP1
PC104 Interrupt Controller
GP2 USB
GP3 COM4
GP4 COM5
GP8 CompactFlash
RDY/nBSY
GP14
FLASH
GP32
CompactFlash Card Detect
PC104 Interrupts
Any interrupt generated on the PC104 interface will generate an interrupt using GP1 in a level
triggered mode. A register located at 0x30000000 will indicate which PC104 IRQ generated the
interrupt. The register indicates the status of the interrupt lines at the time the register is read,
the relevant bit is set to a 1.
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