
Pin Assignment
No. 5557-2/30
LC74794, 74794M
Pin Functions
Pin no.
Pin
Function
Notes
1VSS1
Ground
Ground connection (digital system ground)
2
XtalIN
Crystal oscillator
These pins are used either to connect a crystal and capacitor to form an external crystal
3
XtalOUT
(MUTE input)
oscillator to generate internal synchronizing signals, or to input an external clock signal (2fsc
(MUTE)
or 4fsc). As a mask option, the XtalOUT pin can be set to function as the MUTE input pin.
When the MUTE pin is set low, the video output is held at the pedestal level. (A pull-up
resistor is built in so the input has hysteresis characteristics.)
Switches the mode between external clock input and crystal oscillator operation. A low level
4
CTRL1
Crystal oscillator input switching
selects crystal oscillator operation and a high level selects external clock input. As a mask
(CHABLK) (CHABLK output)
option, the CTRL1 input pin can be set to function as the CHABLK (character border)
output. This is a 3-value output.
5
CS2
Enable input 2
PDC/VPS data output enable input. Data output is enabled by a low-level input. (A pull-up
resistor is built in so the input has hysteresis characteristics.)
6
SCLK2
Clock input 2
Clock input for PDC/VPS data output
(A pull-up resistor is built in so the input has hysteresis characteristics.)
7
DOUT
Data output
PDC/VPS data output
(This is either an n-channel open-drain output or a CMOS output.)
Outputs the state of the external synchronizing signal presence/absence judgment.
8
SYNCJDG
External synchronizing signal judgment
Outputs a high level when synchronizing signals are present.
output
Outputs the crystal oscillator clock when CS1 is low and RST is low. (This signal is not
output on command resets.)
Continued on next page.