Edid Data Write Protect Control Function - NEC LCD1550X Service Manual

1.5.3

EDID data write protect control function

List of control signals
µ-COM Pin No.
I/O
O /WP
37
I P_ID0
43
I P_ID1
42
I P_ID2
41
I P_ID3
40
Function
An EDID data write protection function is provided to prevent the monitor's EDID data from
being damaged by an external source. However, to enable writing of the EDID data in the
production process, the EDID data write protection can be set or canceled (only when the
monitor power is ON) by using the DDC2BI or DDC CI function with the DDC communication
line, or by using the factory 1 OSM function. The DDC2BI or DDC CI function is supported by
the DVI-I connector (D-SUB connector supports only DDC2B), so the EDID data write protec-
tion for EEPROM at the D-SUB connector side must be set and canceled via the DVI-I connec-
tor. Internally, by setting the microcomputer's pin 37 /WP port to Lo, the EDID data write
protection will be set. This will be canceled when set to Hi. /WP is fixed to Lo when the moni-
tor power is OFF. The default value for /WP when the monitor power is ON is Lo. The value is
not saved even when changed, so once the AC power is turned OFF, the value will return to
the default value Lo.
DVI-I connector side EDID data R (Read) / W (Write) ability
DVI external power + 5VDC
(Hi : Asset management = ON)
Lo
Hi
X
X
D-SUB connector side EDID data R (Read) / W (Write) ability
D-SUB external power + 5VDC
(Hi : Asset management = ON)
Lo
Hi
X
X
Signal name
EDID data write protect setting: Lo/Cancel: Hi
LCD panel module setting
Monitor internal power Microcomputer port /WP
(Hi : Monitor AC = ON) (Lo : Protect = ON)
Lo
Lo
Hi
Hi
Monitor internal power Microcomputer port / WP
(Hi : Monitor AC = ON) (Lo : Protect = ON)
Lo
Lo
Hi
Hi
Function
DIGITAL E2PROM
R disabled / W disabled
Lo
R enabled (when selected)
Lo
/ W disabled
R enabled (when selected)
Lo
/ W disabled
R enabled (when selected)
Hi
/ W enabled
Lo
Lo
Lo
Hi
1 - 29
Remarks
M24C02WMN6T
Pull-up / Pull-down
DVI-I connector side
ANALOG E2PROM
R disabled / W disabled
R enabled (when selected)
/ W disabled
R enabled (when selected)
/ W disabled
R enabled (when selected)
/ W enabled
D-SUB connector side
ANALOG E2PROM
R disabled / W disabled
R enabled / W disabled
R enabled / W disabled
R enabled / W enabled