To do this, you may need to dig into the display driver and the sa1100 (or sa1110) datasheet from developer.intel.com.

1. disable the LCD controller (clear the LEN bit in LCCR0)
2. set bits 0 and 9 in PPDR (leaving the rest as-is), configuring LCD data line 0 and the LCLK (line clock) lines on the LCD interface as outputs. The PPSR allows you to set the state of these outputs.

WARNING! Incorrect setting of the PPDR could cause hardware damage - in theory, at least. If you disabled (say) UART3 and enabled the RX3 pin as an output then it would be driving against the serial receiver chip. Not good. We use the PPSR in its default state - ie 0. Setting bits 0 & 9 is no problem, as these are already outputs. The errant behaviour you sometimes see on the standby LED is from the LCD controller still running and occasional mirroring of LDD0 onto the display when LCLK is high.

Normal behaviour (blinking LED) is achieved by having LCLK low (bit 9 of PPSR). If you put LCLK high, the LED will mirror the state of LDD0 (bit 0 of PPSR) - ie, bit 0 high is LED ON, bit 0 low is LED OFF.

With some playing around you can do PWM on the LDD0 line and make the LED do whatever you want.

The LED is not controllable when the display is on, as the display PIC (which also controls the LED) is busy with more important business - like syncing the display up.

Hugo