The file display.c produces an SPI output that drives the GFX1.  This program
runs at 12 MHz on a Silicon Laboratories (Silabs) C8051F320, equivalent to
130208 bytes/second.  The bitmaps show the difference between Bit Bang and
hardware SPI with a clock speed of 3 MHz and illustrates the relationship
between Data and Clock necessary to drive the GFX1 which you must remember
is NOT A SPI device.  Configuration for the SPIO Bus was 3-wire Master Mode
with data centered on the second edge of SCK period and the SCK line high in
idle state.

At 12 MHz the SPI signal (i.e. 8 clock pulses) takes  2.52uS with a space
between signals of 5.16us.  When the clock was increased to 24 MHz then
communications failed.  These figures are offered as an insight into the data
performance, and, may be bettered with a different processor where the
hardware can be configured to better meet the GFX-1 timing diagrams.

The commented out code shows the bit bang software, which is the same as that
used with the other PIC software examples.