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Serial Communication (SCOM) Interface
JH SCOM A1 & C1 Control Interface
This document defines the electrical signals, connectorization, serial data format, and
communication protocol of the A1 and C1 version Serial Communication Control Interface.
Difference between A1 and C1 is that C1 version provides filtered Dsub contacts for military
applications. The purpose of this interface is to provide means for a computer application to control
the LCD backlight and menu of one or more displays.
Interface configuration
The serial interface can have different configurations, selected by three switches.
The configurations are defined as follows:
RS 232
RS 485
Half duplex One computer controls max 16 Displays, each with individual address.
Full duplex
Brightness Control Operation
The backlight brightness at the Display can be controlled in two modes. A serial interface is used to
command the level of backlight brightness and to select mode.
1) Using the local manual brightness control, an operator is only able to adjust brightness to levels
lower than the set maximum, including dimming the backlight to extinction.
2) Brightness is independent of local manual brightness control, set by remote control only.
Electrical Interface
Electrical signals shall conform to RS-485, RS-422 or RS-232. Only Receive Data, Transmit Data,
and Signal Ground are used. The same conditions apply for both RS-422 and RS-485, and will
just be referred to as RS-485 further on in this document. Hardware handshake is only supported
by loopback handshake for RS-232.
Dual 232 and 485 Electrical Interface
Of the two types of electrical interfaces 232 and 485, only one type shall be connected in a given
installation, not both. Both receive and transmit capabilities shall be supported. 485 interface
supports both half and full duplex. Electrical interface and duplex are selected with switches at the
back of the display
Cable
A cable with an overall shield terminated at the back shell should be used.
Communication Interface
IND100084-1
One computer controls one Display, no individual address
65
INB100005-3 (Rev 9)
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