User Guide

The External_Control Protocol
114
Axcess Programming Language
For example, the following command packet (TURN CHANNEL ON) causes channel 4 on device
3 to be turned on (the bytes are shown in hexadecimal):
<$2A> <$Ø1> <$Ø3> <$Ø4> <$32>
The attention byte appears first. Next, the first command ($Ø1) is needed to turn a channel on. The
following two bytes are the device number and channel to be activated. Finally, the checksum
appears at the end.
In this example, the string AMX is sent to device 3:
<$2A> <$Ø4> <$Ø3> <$Ø3> <$41> <$4D> <$58> <$1A>
The attention byte remains the same as before, but the command changes to $Ø4, to tell Axcess to
send a string. The device number is next, followed by the number of bytes comprising the string-in
this case, 3. The hexadecimal values for each letter of AMX is next, and the packet ends with the
checksum.
Responses from Axcess
In the previous sections, a command was sent to the Central Controller. In turn, the Central
Controller also responds to some of the commands. Figure 70 lists the responses. For example, after
you sent the string AMX to the Central Controller, you would receive the following packet if the
transmission was successful:
! <$26> <$Ø4> <$Ø3> <$Ø3> <$41> <$4D> <$58> <$1A>
Command packets (Cont.)
Command Packet structure
SET BYTE LEVEL
'*' <13> <DEVICE> <ADDRESS> <VALUE> <CHECKSUM>
SET WORD LEVEL
'*' <14> <DEVICE> <ADDRESS> <VALUE.2> <CHECKSUM>
LEVEL REQUEST
'*' <15> <DEVICE> <ADDRESS> <CHECKSUM>
$2A (*) is always for sending commands, and $26 (&) is always for responses
Returned packets
Response Packet structure
CHANNEL IS ON
'&' <1> <DEVICE> <CHANNEL> <CHECKSUM>
CHANNEL IS OFF
'&' <2> <DEVICE> <CHANNEL> <CHECKSUM>
RECEIVE STRING
'&' <4> <DEVICE> <# OF BYTES> <STRING> <CHECKSUM>
GET PUSH
'&' <6> <DEVICE> <CHANNEL> <CHECKSUM>
GET RELEASE
'&' <7> <DEVICE> <CHANNEL> <CHECKSUM>
GET DEVICE ID
'&' <8> <DEVICE> <DEVICE ID> <CHECKSUM>
GET BYTE LEVEL
'&' <13> <DEVICE> <ADDRESS> <VALUE> <CHECKSUM>
GET WORD LEVEL
'&' <14> <DEVICE> <ADDRESS> <VALUE.2> <CHECKSUM>
GET LEVEL
'&' <15> <DEVICE> <ADDRESS> <VALUE.2> <CHECKSUM>