Specifications

Danish Interpretation Systems Technical Specifications
Printed in Denmark
50
6 Additional detailed example
6.1 Example - Registration with the CU
The first example shows how registration with the CU is done from AMX. The AMX equipment is
connected to the CU via the RS232 connection. The CU has already been powered up.
Three steps must be passed:
- Step (1) - The CU must be put in Microphone Control Mode
- Step (2) – A registration request must be transmitted from AMX
- Step (3) – The registration reply is received in AMX
6.1.1 Step (1) – Entering Microphone Control Mode
Entering the microphone control mode is done by sending a ‘Change Binary Control Mode’ message.
Below, the contents of the control message for entering the microphone control mode is decided, step-
by-step as explained in 3.5.
Step (1.A) – Decide the Message Type and contents
From chapter 3.4.2 the Message Type is ASCII character ‘m’, which corresponds to the binary value
<109> or hexadecimal value [0x6D].
The contents are also found in chapter 3.4.2 to be ‘c’ ‘m’.
Step (1.B) – Decide the ID of the message
The ID of a control message indicates, which number the message has in a sequence of messages sent
from the AMX to the CU.
For this example, the ID is given the value <0>.
Now, the unfinished control message looks like this:
‘m’ <0> ‘c’ ‘m’
Step (1.C) – CRC calculation
In order to prevent transmission errors, a CRC-check sum is added to the control message.
CRC calculation is done byte for byte starting with CRC-value=0 and the first byte (‘m’). These are
exclusive or’d and used as index in the lookup table.
Going byte by byte gives the following table of results: