User Manual DEV 1953
110
Copyright DEV Systemtechnik GmbH 2015-2017
5.8.3.2
Check Queue (Q)
The command for reading the change queue is issued in the form
hexadecimal:
02 XX XX 51 03 XX
content:
<STX> <address> Q <ETX> <checksum>
e.g. for a device that is connected via Ethernet
hexadecimal:
02 46 46 51 03 50
content:
<STX> <address=FF> Q <ETX> <checksum>
The change queue contains up to 8 changes on the switching status of the device
that were executed since the last
Q
command was issued. Only the last change will
be stored in the queue if more than one change is executed for a certain output
port. The ASCII byte (
<chgs>
) after "
Q
" in the positive response is the number of
changes that the queue contains in the range 0…8, i.e. 0x30…0x38. If no changes
are stored in the queue, this number is 0; if more than 8 changes have occurred
since the last Q command was issued, this number will not be valid and bit 3 of the
queue change flag (please refer to chapter 5.8.3.1) is set for the indication of an
overflow of the change queue. After the queue is checked via the
Q
command, the
queue and the queue change flag are cleared.
In the positive response to this command each change in the queue delivers 6 bytes
reporting the output port number and the input port number to which the output
port is currently connected to
("
⌡
" and "
⌠
" are symbolizing that the two consecutive lines are actually one line).
hexadecimal:
06 XX XX 51 XX XX XX XX
⌡
content:
<ACK> <address>
Q <chgs> <output=ooo
1
>
⌡
hexadecimal:
⌠
XX XX XX
(…) XX XX XX XX XX XX
⌡
content:
⌠
<input=iii
1
>
(…) <output=ooo
chgs
> <input=iii
chgs
>
⌡
hexadecimal:
⌠
03 XX
content:
⌠
<ETX> <checksum>
e.g. for a device that is connected via Ethernet with no changes
hexadecimal:
06 46 46 51 30 03 64
content:
<ACK> <address=FF> Q 0 <ETX> <checksum>
and e.g. for a device that is connected via Ethernet with a single change (output
port 1 connected to input port 2)
hexadecimal:
06 46 46 51 31 30 30 31
⌡
content:
<ACK> <address=FF> Q 1 <output=001>
⌡
hexadecimal:
⌠
30 30 32 03 66
content:
⌠
<input=002> <ETX> <checksum>
