mc68hc908bd48 Freescale Semiconductor, Inc, mc68hc908bd48 Datasheet - Page 214

• Manufacturer Part Number: mc68hc908bd48
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Sync Processor
16.5.1 Polarity Detection
16.5.1.1 Hsync Polarity Detection
16.5.1.2 Vsync Polarity Detection
16.5.1.3 Composite Sync Polarity Detection
Data Sheet
214
The Hsync polarity detection circuit measures the length of high and low
period of the HSYNC input. If the length of high is longer than L and the
length of low is shorter than S, the HPOL bit will be "0", indicating a
negative polarity HSYNC input. If the length of low is longer than L and
the length of high is shorter than S, the HPOL bit will be "1", indicating a
positive polarity HSYNC input. The table below shows three possible
cases for HSYNC polarity detection — the conditions are selected by the
HPS[1:0] bits in the Sync Processor Control Register 1 (SPCR1).
The Vsync polarity detection circuit performs a similar function as for
Hsync. If the length of high is longer than 4ms and the length of low is
shorter than 2ms, the VPOL bit will be "0", indicating a negative polarity
VSYNC input. If the length of low is longer than 4ms and the length of
high is shorter than 2ms, the VPOL bit will be "1", indicating a positive
polarity VSYNC input.
When a composite sync signal is the input (COMP = 1 for composite
sync processing), the HPOL bit = VPOL bit, and the polarity is detected
using the VSYNC polarity detection criteria described in section
16.5.1.2.
Long is greater than (L)
3.5µs
14µs
Polarity Detection Pulse Width
7µs
Sync Processor
Short is less than (S)
12µs
6µs
3µs
MC68HC908BD48
Freescale Semiconductor
HPS1
SPCR1 ($0046)
0
1
0
—
HPS0
Rev. 2.1
0
X
1