NEC NEC MultiSync LCD1550X LCD1550X LCD1550X, Service Manual

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1.4.7 Input signal switching control function
Functions
• H, V Sep, and C/S and S/G input switching
When using analog signals, the microcomputer uses the selector to change the signal path
input into the ASIC AH* terminal according to the input signal judgment results.
• Analog signal DVI-I (A) and analog signal D-SUB input selection
The microcomputer sets the ASIC internal input switching switcher (SOURCE register) to
"analog 1" for DVI-I (A) and to "analog 2" for D-SUB.
The video buffer output control follows the table below. Only the input and displayed Ch side is
enabled with this, and video is input into ASIC (measures for crosstalk during ASIC 2Ch input).
µ-COM Pin No.
47 ~ 51
7
8
33
19
I / O
I / O
O
O
O
O
Signal name Remarks Function
MS*, RSTN
SEL_HS1_SG1
SEL_HS2_SG2
SEL_1
SEL_2
ASIC
74ACT157SJ
74ACT157SJ
Video buffer
Video buffer
ASIC control
H, V Sep, and C/S and S/G input switching
H, V Sep, and C/S and S/G input switching
DVI-I (A) path video buffer output control
D-SUB path video buffer output control
List of control signals
SEL_1, SEL_2
Lo
Hi
Video buffer output
Disable (Equivalent to GND pull-down at 120
Ω
)
Enable (video through)
Input signal judgment results
SEL_HS1_SG1
(AH1 path selection)
Lo
Hi
Don't Care
Don't Care
SEL_HS2_SG2
(AH2 path selection)
Don't Care
Don't Care
Lo
Hi
* If the signal is displayed and selected when changing the path, it will be judged that the
signal has changed, and the mode will be changed.
No S / G in DVI-I (A)
S / G present in DVI-I (A)
No S / G in D-SUB
S / G present in D-SUB