mc68hc05bs8 Freescale Semiconductor, Inc, mc68hc05bs8 Datasheet - Page 80

• Manufacturer Part Number: mc68hc05bs8
• Description: Mc68hc05 Family Of Low-cost Single-chip Microcontrollers.
• Manufacturer: Freescale Semiconductor, Inc

9
9.5
Figure 9-2 is a block diagram of the Sync Separator which includes the duration counters for the
high and low pulses, a counter for the number of valid horizontal sync pulses, a register to hold
the number of horizontal lines per frame, a logic block for horizontal and vertical sync pulse
separation, a comparator, and a sync pulse insertion circuit.
The Low pulse duration counter examines the low pulse width of the incoming composite sync
signal. If it is within the horizontal sync pulse limit (8 s or 16 t
detected, and the horizontal line counter is advanced. If the low pulse is wider than the limit, a
vertical sync pulse is detected, and the content of the Horizontal line counter is loaded into the
Horizontal Line register. The Low pulse duration counter then resets the Horizontal line counter.
The High Pulse Duration Counter examines the high pulse width of the incoming composite sync
signal. If it is longer than a specific value (8 s or 16 t
a “finish” signal will be given to the Sync Separation Logic.
Sync Separation Logic passes the Csync signal to the Hsync output until there is an “equal” signal
from the comparator. The Hsync output will then output an reassembled waveform by the Sync
Insertion Circuit to emulate the Hsync pulses, and the Vsync output is set to “low” at the coming
falling edge of the Csync signal. After the “finish” signal has been sensed, the Vsync output is fixed
to “high”, and the Hsync output follows the Csync input again.
9-4
CLK
Csync
High pulse duration counter
Low pulse duration counter
Sync Separation
SYNC SIGNAL PROCESSOR
Figure 9-2 Sync Separator
finish
Csync
Horizontal Line counter
reset
load
CYC
count
), the vertical sync pulse has finished and
Hsync
Sync separation logic
Sync insertion circuit
CYC
Comparator
Vertical
), a horizontal sync pulse is
equal
in
Vsync
Horizontal Line Register
MC68HC05BS8
out
TPG