Rev. 1.0, 02/00, page 787 of 1141
(2) Inputting the Csync Signal as the Source
When the Csync signal is selected as the source, the Vsync component can be processed in two
methods: using the Vsync Schmitt circuit or using the Csync Schmitt circuit.
(a) Using the Vsync Schmitt Circuit
The Csync signal having the polarity selected by the SYNCT bit (bit 4) of the SEPIMR is
input to the Csync/Hsync terminal. The Hsync component is input through the Csync
Schmitt circuit to the digital H separation counter; the Vsync component goes through the
external LPF circuit, then is input through the Vsync/VLPF terminal and the Vsync
Schmitt circuit to the digital V separation counter. Figure 27.17 shows this method.
CVin2
Csync
a
1
1
0
0
b
a
b
Hsync
Vsync
VLPF
Vsync/VLPF
Csync/Hsync
Hsync
Vsync
External
SW3
Internal
SW5
External
SW2
External
SW1
Reference
voltage switch
Register
control
I/O switch
I/O
switch
Polarity
switch
Polarity
switch
Digital H
separation
counter
Digital V
separation
counter
DLPFON
Csync polarity
Schmitt circuit
Vsync polarity
Schmitt circuit
External circuit
Inside LSI
Csync
separation
comparator
External
SW4
CVin2
–
+
CCMPSL
CCMPV0, 1
SYNCT
VSEL
SEPV
SEPH
Sync tip
clamp
Internal
SW6
Figure 27.17 Sync Source Selection When Using the Csync Signal and
the Vsync Schmitt Circuit
Source
Signal
Vsync
Detection
External
SW1
External
SW2
External
SW3
External
SW4
CCMPSL
(Internal
SW5)
VSEL
(Internal
SW6)
Csync/
Hsync
Terminal
I/O
Csync
input
Vsync
Schmitt
On
On
a
a
1
0
Input