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Signals
2-9
MC68328 USER’S MANUAL 11/6/97
MOTOROLA
SIGNAL
DESCRIPTIONS
2
PRELIMINARY
PG3/TOUT2 —TIMER 2 OUTPUT, PORT G 3
This bidirectional signal can be programmed to toggle or generate a pulse of one system
clock duration when timer/counter channel 2 reaches a reference value. By default after
reset, this pin becomes general-purpose input, PG3.
2.1.14 PWM Pin
PG2/PWMO—PULSE WIDTH MODULATOR OUTPUT, PORT G 2
This pin can serve as the PWM output signal. When it is PWMOUT, it produces synthesized
sound, which can be connected to a filter and audio amplifier to generate melody and tone.
By default after reset, this pin becomes general-purpose input, PG2.
2.1.15 Real-Time Clock Pins
PG7/RTCO—REAL-TIME CLOCK OUTPUT/INPUT, PORT G 7
While PC0/MOCLK is high, this pin is a dedicated input that provides the 32.768 kHz or 38.4
kHz clock to the real-time clock. While PC0/MOCLK is low, this pin can be programmed to
output constant time tick pulses at the crystal frequency. By default after reset while PC0/
MOCLK is low, this pin becomes general-purpose input, PG7.
2.1.16 LCD Controller Pins
LD3-LD0—LCD DATA BUS
This output bus transfers pixel data to the LCD panel for display. The pixel data is arranged
to accommodate the programmable panel mode data width selection. Panel interfaces of
one, two, or four bits are supported. Users can also program the output pixel data to be
inverted for those LCD panels that require it.
The MC68328 LCD interface data bus uses LD0 to display pixel 0, 0. Some LCD panel
manufacturers specify their LCD panel data bus where data bit 3 of the panel displays pixel
0,0. For these panels, the connections from the MC68328 LD bus to the LCD panel data bus
are reversed in bit significance. Therefore, for these panels, connect LD0 of the MC68328
to LCD panel data bit 3, LD1 to LCD data 2, LD2 to LCD data 1, and LD3 to LCD data 0.
LFLM—FIRST LINE MARKER
This signal indicates the start of a new display frame. LFLM becomes active after the first
line pulse of the frame and remains active until the next line pulse, at which point it de-
asserts and remains inactive until the next frame. LFLM can be programmed to be an active-
high or an active-low signal.
LP—LINE PULSE
This signal latches a line of shifted data onto the LCD panel. It becomes active when a line
of pixel data is clocked into LCD panels and remains asserted for 8 pixel clock periods. LP
can be programmed to be either an active-high or an active-low signal.