Philips DVDR615 Service Manual page 139

http://www.jdwxzlw.com/?fromuser=华盛维修
Circuit-, IC descriptions and list of abbreviations
The voltage detector NCP303LSN290 [7926] provides the
reset signal PNX7100_RESETn (active: low) with the correct
timing behavior. This circuitry functions as a Power-On Reset
(POR) module, which detects the minimum functional voltage
that is needed by the device. It also detects any voltages drop.
When the power voltage is outside the nominal range, a reset
signal is generated by the POR module and fed to the reset
module which controls the individual reset of the different
peripherals and processing units.
There are two control lines which can overrule this reset signal:
• IRESET_DIG (controlled by the slave µP on the MOBO
Analog board)
• EJTAG_RESETn (only for production)
They can pull the output of the NCP303LSN29 [7926] down via
a shottky diode.
So when the output signal PNX7100_RESETn is low, the board
will reset. When this signal is high, the board is up and running.
The PNX7100_SYS_RESETn is a general enabling signal for
the different reset lines. All other reset lines are directly driven
from Chrysalis [7800] port pins (eg. MPIO13_IDE1_RESETn).
All reset lines are logically connected via 74LVC08AD [7923]
AND-gates. If both reset signals are low, all other external
devices are initialized.
2
I C Bus
The Chrysalis [7800] is the master of all the I
2
reset, external I C masters are allowed). The following ICs are
2
controlled by the I C bus:
• [7904] Boot Eeprom
• [7905] NVRAMs
• [7007] VIP
9.2.5 I/O Connectors
Audio IO Connector [1902]
The Audio In/Out (AIO) connector is used to interchange digital
audio signals between MOBO Analog and FEBE Backend
Digital portion.
Video IO Connector [1901]
The Video In/Out (VIO) connector is used to interchange
analogue video signals between MOBO Analog and FEBE
Backend Digital portion.
9.2.6 Service UART Interface
Transistor 7950, BC847BS is used to make a level conversion
from microprocessor (LVTTL) to +/-5V (compatible with most
RS232 interfaces) and vice versa. The control line
MPIO19_CTL_SERVICE is used to activate service and
diagnostic SW at start up procedure. The connectivity is
provided via an external service tool.
家电维修资料网，免费下载各种维修资料
2
C bus (during
DVDR615/69 9. EN 139