Philips FM24 Service Manual page 105

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Introduction
The FM24 monitor is equipped with an RS232 interface. Via a
9 pin Sub-D connector, it is possible to connect a PC for special
modes like:
• SW download.
• Factory purposes.
• Service.
• Professional use.
A second option is the connection of a so-called ICONN-box for
Institutional TV (Hotel TV).
For communication with the Receiver Box, UART is used,
because this protocol can handle longer cable distances than
2
I C. The (Receiver box) UART is interfaced via a 15 pin Sub-D
connector (VGA connector). Via this UART connection, the
F21RE Receiver box and the FM24 Monitor can communicate
(via FSP). By doing so, the monitor will know that there is an
Receiver box connected and thus it is operating as a TV
configuration.
RS232/UART Control
The OTC (SELECT_1 to 4) controls the RS232/UART
switches. When the monitor is in Receiver box mode, there is
no RS232 communication possible. The monitor is default set
in Receiver box mode (switch to n.c. position) and the UART
from/to VGA1 is enabled, to allow communication with
Receiver box.
If no Receiver box is detected, the UART is disabled to ensure
that there will be no communication towards the OTC, and the
switch is set to OTC. Below the truth table of the switches is
shown, which determine the TXD/RXD path.
Table 9-7 RS232/UART Control
0 0
0 0
0 0
0 0
0 1
0 1
0 1
0 1
1 0
1 0
1 0
1 0
1 1
1 1
1 1
1 1
(1) Software download or ComPair mode.
(2) Software download or Debug mode.
(3) When S3 = 1 the 74HCT4052 is in a tri-state ('off' state).
(4) When S4 = 0 the TXD out of RS232 is disabled (S4 may not
become low in any other case).
UART Detection
When the VGA1_RXD line is continuously 'low', the OTC might
run slow due the fact that so-called 'break' signals are
Circuit Descriptions and List of Abbreviations
0 0 0 0 0
0 1 0 0 0
1 0 0 0 0
1 1 1 0 0
0 0 0 0 0
0 1 0 0 0
1 0 0 0 0
1 1 1 0 0
0 0 0 0 0
0 1 0 0 1
1 0 0 1 0
1 1 0 0 0
0 0 0 0 0
0 1 0 0 0
1 0 0 1 0
1 1 0 0 0
Digitized in Heiloo, Holland
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
FM24
generated. To prevent this, a small circuitry is added to detect
whether VGA1_RXD is continuously 'low' (item 7310).
When the VGA1_RXD line is 'low' for about 20 ms, the buffer-
switch (item 7303-A) is opened. After this buffer, a second
discrete buffer is placed (items 7315/16), which keeps the
RXD_OTC line 'high' and changes the 5 V into a 3.3 V level.
ICONN-box
For application of a Flat TV in a hotel environment, the monitor
is designed to operate with a so-called ICONN-Box. The
ICONN-box will take over the user control of the monitor, by
intercepting the RC5-commands coming from a dedicated RC-
transmitter, which sends specific hotel-mode commands and
sending its own RC-commands to the microprocessor in the
monitor.
So in the ICONN-Box, the hotel-mode commands will be
converted to RC5-commands, which than can be interpreted by
the monitor.
When connected to the RS232 input, this box takes over the
control of the IR-receiver in the monitor. It is also able to control
the front LED. The switches (7550 for the IR and 7555 for the
LED signals) are controlled by the ICONN_NOT signal.
The ICONN-Box shall interface the Monitor with the following
signals:
• IR-RX. These are the RC5-commands coming from the
specific hotel RC5 - transmitter, which are received via the
RC5-receiver of the monitor.
• IR-TX. These are the RC5-commands generated by the
ICONN-Box and send to the monitor.
• RL-ICN. Control signal from the microprocessor (of the
monitor), indicating the power state of the monitor. The
ICONN-Box and monitor LED are driven in parallel.
• GL-ICN. Control signal from the microprocessor (of the
monitor), indicating the functionality of the monitor, to drive
the LED on the ICONN-Box.
• LD-ICN. Control signal from the ICONN-Box to drive the
green LED on the monitor.
31/8/2014
9. EN 105