EMBRON HATTELAND TECHNOLOGY X MMD G2 Series, Техническое руководство

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IND100084-17
Introduction
This document defines the electrical interface, serial data format, and communication protocols of the Serial
Communication Control Interface (SCOM). The purpose of this interface is to enable a computer application to control
one or more units. Unit refer to display product. Interface configuration done within OSD Menu.
Serial / USB Interface Configuration
The serial / USB interface can have different configurations defined as follows:
RS-232 One computer controls one unit, no individual address
USB One computer controls one unit, no individual address
4-wire RS-485/RS-422 One computer controls units, each with individual address.
2-wire RS-485 One computer controls units, each with individual address.
Each unit will be assigned with an address value before it is connected to a shared network. The user application
(PC) can send the message to the specific unit by marking the message with corresponding address number. The
unit which has the matching address will respond immediately, while the others keep silent.
Broadcast commands will be processed by all linked units simultaneously once the last byte of the message is
received. In order to avoid confliction on bus, each unit should respond back at different times. As the units are
working independently, they can hardly know how many units are linked in the same bus. In this case, the interval
between receiving message and responding back should be calculated in the base of their own address. The lowest
addressed unit will respond first.
To calculate the address based interval, there is a formula to calculate the interval (Te):
Te = (Tr +Lr) * N, where
Lr = length of the ACK/NAK message response
Tr = Response time
N = the total number of monitors
Response time Tr is a fixed value which are calculated to make sure there is no conflict on the bus. Principally, Tr is
equivalent to 2.5 byte periods after the last byte of a command message is received. However, due to the difference
in microcontroller clock, all the units may not finish the message receive at the same timing point. So the Tr should be
calculated based on the jitter changes.
Illustration: Broadcast Message: Timing 1
Serial/Ethernet/USB Communication (SCOM) Interface